K20 frame with K10 axles? any problems here?

[Nasty-LSX]

Ok, remember folks, Im out of my knowledge area here. All 4x4 stuff is new to me.

I found a guy local that deal's with all C10 K10 K20 K30 and so. I dont know whats all compatible
and interchangeable. He says he has a 84 K20 frame complete and axles from a 70's something blazer 6/lug. In my mind I dont see why the axles wont just bolt right up. Im not worried about the
springs because I will buy new one's from front to back. So my questions are......

1. Even though its a K20 frame, I should be able to buy stock 1500 replacement springs and install with no issue's?
2. I believe the only difference from a K20 frame and 1500 is thickness?
3. Is there anything I need to look out for when I purchase? and how to make sure it's a 81/87
frame? I told him that 70's frame would not work I needed a 81/87 and he said it was a 70's front clip swap. To look at the front bumper horns, it was a 84 frame.
4. were the 70's front and rear axles as good as the 80's axles?
5. Anything im missing here before purchase?

here is the 84 K20 frame

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and here is the 70's something blazer.

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[PrairieDrifter]

70's axles are better in my opinion. Rear leaf spring length is the only real difference, 10 will have 52's and 20's and 30's have 56's. Shock mounts may be different.

 

[Nasty-LSX]

70's axles are better in my opinion. Rear leaf spring length is the only real difference, 10 will have 52's and 20's and 30's have 56's. Shock mounts may be different.

Damn, I knew something would be off. I believe k20 have a rougher ride than the K10, And yup, shock mount could be a problem. Lets see if someone chimes in on that. Thanks

 

[Strick]

The 10 & 20 frames are alike as far as I know. The 30 is definitely different.

HS

 

[AuroraGirl]

Damn, I knew something would be off. I believe k20 have a rougher ride than the K10, And yup, shock mount could be a problem. Lets see if someone chimes in on that. Thanks

4wd frames should be the same functionally between k10 and k20

Ive heard 2wd frames may be thinner but these are both 4wd so that helps. 4wd half tons are 6 bolt you know that
and the springs will be a difference, as well as brakes (obv) but you are basically downgrading the k20 to a k10, right? So you should be ok

 

[legopnuematic]

Some 1/2 tons have 56” springs and some 3/4 tons have 52” springs, however the front spring mount is the same, it’s the rear mount that moves to accomplish the difference in length, and the frame should already have both sets of holes.

Some aftermarket rear shackle mounts (like ORD’s) can be swapped side to side to use 56” or 52” springs in the 52” spring holes.

C/K10-20 frames are all 6” tall rails and thicknesses are the same. 30 series frames are 8” tall rails and slightly thicker.

Frame horns are the easiest way I know of to tell 70s vs 80s frame. 70s are nice and rounded and 80s are slash cut.

Theres debate on if a 10 bolt is better than a 12 bolt or the other way round. My opinion is both are fine if in good health for most peoples uses. Being a K series, you have the option to put a 9.5” 14 bolt semi float from a GMT400 under the rear, 8 or 6 lug variants are out there (make sure it came from a 4wd, 2wd’s are 3” narrower DAMHIK). This requires putting new shock mounts and spring perches of course, but is a substantial axle for what it is. Currently building one for a friends 75 K5.

I believe the front on 70s K10 should be a Dana 44(?) and the 80s is a 10 bolt. Once again, really a wash on what is better, both have advantages and disadvantages I’d say.

Stock to stock the shock mounts should be the same (frame is certainly the same), with a lift that may require alterations on the axle to keep things from binding up.

 

[AuroraGirl]

Some 1/2 tons have 56” springs and some 3/4 tons have 52” springs, however the front spring mount is the same, it’s the rear mount that moves to accomplish the difference in length, and the frame should already have both sets of holes.

Some aftermarket rear shackle mounts (like ORD’s) can be swapped side to side to use 56” or 52” springs in the 52” spring holes.

C/K10-20 frames are all 6” tall rails and thicknesses are the same. 30 series frames are 8” tall rails and slightly thicker.

Frame horns are the easiest way I know of to tell 70s vs 80s frame. 70s are nice and rounded and 80s are slash cut.

Theres debate on if a 10 bolt is better than a 12 bolt or the other way round. My opinion is both are fine if in good health for most peoples uses. Being a K series, you have the option to put a 9.5” 14 bolt semi float from a GMT400 under the rear, 8 or 6 lug variants are out there (make sure it came from a 4wd, 2wd’s are 3” narrower DAMHIK). This requires putting new shock mounts and spring perches of course, but is a substantial axle for what it is. Currently building one for a friends 75 K5.

I believe the front on 70s K10 should be a Dana 44(?) and the 80s is a 10 bolt. Once again, really a wash on what is better, both have advantages and disadvantages I’d say.

Stock to stock the shock mounts should be the same (frame is certainly the same), with a lift that may require alterations on the axle to keep things from binding up.

squares also came with 14 bolt semi floats

 

[legopnuematic]

squares also came with 14 bolt semi floats

This is true, the appeal of the 400 swap is that they are about 1” wider flange to flange than a squarebody rear, so if you are like my friend who absolutely hates that squarebodys track width is narrower in the rear, the later 9.5 eliminates the need for spacers like he has now on his 10 bolt.
The other thing is since the GMT400 9.5 can be found with 6 or 8 lug, that means the 6 lug 15” slot mags can stay without redrilling or having custom axle shafts made.

 

[Strick]

I used many parts on my '55 6100 truck. A '76 K20 frame with an '04 G3500 rear axle and 10 bolt 8-lug front axle. Here is a pic of how much wider the rear track width with the 14FF installed. There are 37x12.50 16.5 BFG's mounted on the axle in the pic.

HS

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[AuroraGirl]

I used many parts on my '55 6100 truck. A '76 K20 frame with an '04 G3500 rear axle and 10 bolt 8-lug front axle. Here is a pic of how much wider the rear track width with the 14FF installed. There are 37x12.50 16.5 BFG's mounted on the axle in the pic.

HS

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AAm 11.5?

 

[Strick]

Corporate 14FF still. My DMAX has that huge 11.5 though.

HS

 

[AuroraGirl]

cant see it but mine ish ere too