New to the forum, but not to Squarebodies...

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BigT

Junior Member
Joined
Oct 17, 2024
Posts
14
Reaction score
39
Location
Selah, WA
First Name
Tim
Truck Year
1978
Truck Model
Scottsdale K20
Engine Size
350
I grew up with Squarebody Chevies, as my dad had 3 or 4 of them over the years; I even learned to drive in a '75 1/2 ton 4X4 manual hauling hay bales. After about 20 years without one around, I recently bought an almost entirely cancer-free '78 Scottsdale K20 for my daily driver. Mildly built 350 w/ 4 bbl Quadrajet, TH400, NP203, and 4:56 gears!! Low, low!! I also have the build sheet, and it's almost entirely stock. Factory A/C (missing a bunch of parts, including the compressor), cruise control (transducer is there, but missing the rest), and the HC4 4:56 gears. The underside of this beast looks new!!
I could use some advice from you squareheads on a couple of things:
1. I know the gears came with the truck, since they are on the build sheet. I looked the truck up on the build option chart posted elsewhere on this forum, and it would appear that they must have been special ordered, as the charts say that gear ratio was only offered stock on the K30 one-tons. Since they were put on this truck by Chevy, does that mean that other rear-end components were likely beefed up as well, or could the 4:56 gears just be paired up with the standard 3/4 ton axles, etc.? I ask because I may want to swap both front and rear gear sets to 4:10s at some point in the future, but I'm not sure what all I will need to do that.
2. Come next summer, I will want to get the A/C working, and I ordered the whole OEM style shooting match from LMC to have on hand when the time comes. LMC did not offer all of the lines, however, as you can see in the attached diagram circled in red. Can you guys tell me what that part is and where I might locate it?
3. I also have no idea which compressor to get. I've never had one of these trucks with A/C in it, so I don't know what I am looking for. Is there one out there that uses the newest refrigerant, or are they all R134A?

Thanks a lot for your help in advance!!

Tim

PS - Yes, I know the grille is not the right one for that truck - it's already been swapped out with the right one, just haven't taken a new pic yet!!
 

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JamesSam

Full Access Member
Joined
Feb 15, 2023
Posts
1,576
Reaction score
4,321
Location
VA
First Name
Sam
Truck Year
1987
Truck Model
Silverado V10
Engine Size
5.7 L 350 v8
Welcome from VA. Awesome truck.
 

legopnuematic

Licensed Junk Dealer
Supporting Member
Joined
Oct 27, 2016
Posts
2,443
Reaction score
6,180
Location
MO
First Name
Spencer
Truck Year
1971, 1̶9̶7̶4, 1976, 1979,1̶9̶8̶5, 2002
Truck Model
Dart Swinger, Sierra 10, C10 Cheyenne, C10 Big Ten, Silverado 10, Ram 2500
Engine Size
225/6, 350 c.i., 350 c.i., 5.9l Cummins
Welcome from Missouri.
 

BigT

Junior Member
Joined
Oct 17, 2024
Posts
14
Reaction score
39
Location
Selah, WA
First Name
Tim
Truck Year
1978
Truck Model
Scottsdale K20
Engine Size
350

WFO

Full Access Member
Joined
Jan 6, 2017
Posts
3,673
Reaction score
5,014
Location
Texas Panhandle
First Name
Dan
Truck Year
1986
Truck Model
K20
Engine Size
350
Welcome from the Texas Panhandle.
 

Grit dog

Full Access Member
Joined
May 18, 2020
Posts
6,906
Reaction score
12,109
Location
Auburn, Washington
First Name
Todd
Truck Year
1986, 1977
Truck Model
K20, C10
Engine Size
454, 350
I grew up with Squarebody Chevies, as my dad had 3 or 4 of them over the years; I even learned to drive in a '75 1/2 ton 4X4 manual hauling hay bales. After about 20 years without one around, I recently bought an almost entirely cancer-free '78 Scottsdale K20 for my daily driver. Mildly built 350 w/ 4 bbl Quadrajet, TH400, NP203, and 4:56 gears!! Low, low!! I also have the build sheet, and it's almost entirely stock. Factory A/C (missing a bunch of parts, including the compressor), cruise control (transducer is there, but missing the rest), and the HC4 4:56 gears. The underside of this beast looks new!!
I could use some advice from you squareheads on a couple of things:
1. I know the gears came with the truck, since they are on the build sheet. I looked the truck up on the build option chart posted elsewhere on this forum, and it would appear that they must have been special ordered, as the charts say that gear ratio was only offered stock on the K30 one-tons. Since they were put on this truck by Chevy, does that mean that other rear-end components were likely beefed up as well, or could the 4:56 gears just be paired up with the standard 3/4 ton axles, etc.? I ask because I may want to swap both front and rear gear sets to 4:10s at some point in the future, but I'm not sure what all I will need to do that.
2. Come next summer, I will want to get the A/C working, and I ordered the whole OEM style shooting match from LMC to have on hand when the time comes. LMC did not offer all of the lines, however, as you can see in the attached diagram circled in red. Can you guys tell me what that part is and where I might locate it?
3. I also have no idea which compressor to get. I've never had one of these trucks with A/C in it, so I don't know what I am looking for. Is there one out there that uses the newest refrigerant, or are they all R134A?

Thanks a lot for your help in advance!!

Tim

PS - Yes, I know the grille is not the right one for that truck - it's already been swapped out with the right one, just haven't taken a new pic yet!!
Wow! Ida kept the 73/74 grille style. Love those.
Someone must’ve put an older core support n stuff in it. As those grilles are not supposed to fit in 75 (I think ) and up trucks because they set deeper than the newer models.
New one bolt right in?

Regarding gears, even if it was special ordered I’m fairly certain the axle is identical. 14bolt full floater.
That said, 4.56 is almost un driveable unless you never get on I 82 and only take back roads at 55mph.
I have 4.10s with new 35s and that is prohibitive for freeway driving imo.
3000rpms at 70mph roughly is what I get, just not conducive for driving the open road. I’d strongly consider you think about 3.73s tops and possibly a little higher even if it’s going to be a go everywhere daily driver.
 

Grit dog

Full Access Member
Joined
May 18, 2020
Posts
6,906
Reaction score
12,109
Location
Auburn, Washington
First Name
Todd
Truck Year
1986, 1977
Truck Model
K20, C10
Engine Size
454, 350
Welcome from Oregon. Dig that visor stuff lol
Yeah, those Lund visors on this style truck look awesome imo.
Although I’m less in favor of them on 2wd trucks. Idk why but I think they look much more at home on 4x4s.
 

Keith Seymore

Full Access Member
Joined
Jul 13, 2015
Posts
2,856
Reaction score
9,068
Location
Motor City
First Name
Keith Seymore
Truck Year
1987
Truck Model
R10
Engine Size
4.3L
I grew up with Squarebody Chevies, as my dad had 3 or 4 of them over the years; I even learned to drive in a '75 1/2 ton 4X4 manual hauling hay bales. After about 20 years without one around, I recently bought an almost entirely cancer-free '78 Scottsdale K20 for my daily driver. Mildly built 350 w/ 4 bbl Quadrajet, TH400, NP203, and 4:56 gears!! Low, low!! I also have the build sheet, and it's almost entirely stock. Factory A/C (missing a bunch of parts, including the compressor), cruise control (transducer is there, but missing the rest), and the HC4 4:56 gears. The underside of this beast looks new!!
I could use some advice from you squareheads on a couple of things:
1. I know the gears came with the truck, since they are on the build sheet. I looked the truck up on the build option chart posted elsewhere on this forum, and it would appear that they must have been special ordered, as the charts say that gear ratio was only offered stock on the K30 one-tons. Since they were put on this truck by Chevy, does that mean that other rear-end components were likely beefed up as well, or could the 4:56 gears just be paired up with the standard 3/4 ton axles, etc.? I ask because I may want to swap both front and rear gear sets to 4:10s at some point in the future, but I'm not sure what all I will need to do that.
2. Come next summer, I will want to get the A/C working, and I ordered the whole OEM style shooting match from LMC to have on hand when the time comes. LMC did not offer all of the lines, however, as you can see in the attached diagram circled in red. Can you guys tell me what that part is and where I might locate it?
3. I also have no idea which compressor to get. I've never had one of these trucks with A/C in it, so I don't know what I am looking for. Is there one out there that uses the newest refrigerant, or are they all R134A?

Thanks a lot for your help in advance!!

Tim

PS - Yes, I know the grille is not the right one for that truck - it's already been swapped out with the right one, just haven't taken a new pic yet!!
Welcome from the Motor City.

At your leisure could you please post up a pic of the build sheet?

K
 

Keith Seymore

Full Access Member
Joined
Jul 13, 2015
Posts
2,856
Reaction score
9,068
Location
Motor City
First Name
Keith Seymore
Truck Year
1987
Truck Model
R10
Engine Size
4.3L
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