is this a Frankentruck?

[J-SQUARED]

Hi all, my name is Josh. I'm new here and just bought a project truck to work on with my son Jacob. I've have done multiple searches on the site and it has been a wealth of knowledge but I have some opinion based questions for the community. The truck is an 85 K1500 reg cab long bed that was mid process with the guy I bought it from. He had multiple projects going at once which is why he cut this one loose. He said he already did a rear main seal. He also did all of the brakes, pressure tested and powder coated the radiator, blasted and powder coated 5 rally wheels, and put on new transmission lines plus some little things here and there. he gave me a very good condition OEM core support, new inner fenders, some interior pieces and parts, and a new energy suspension body mount kit for the cab. He was just starting to remove a 3" body lift. I picked up the truck in a state of partial disassembly so I was not able to drive it but the guy I got it from drove it home from the guy he got it from with no issues. The previous owner had done a lot of body work to it, but hadn't started the rockers or floor boards yet.

you're probably wondering where my question is by now, lol. We hooked up the necessities to start the truck and I confirmed it runs and it also moved forward and backward when I put it in gear in my barn. The VIN number on the RPO sheet, dash, and door sticker all match. I have been doing some research to find it on the frame and cannot seem to find it. All of the info I have found has said on top of the frame rail on either side mid way of the entry door and/or on the front of the frame near the engine mount. Since the truck still has the body lift I actually have access to the top of the frame and cannot seem to find anything. I have found clearly stamped part numbers on the side of the frame. Front half of the frame is 8 out of 10 shape and rear portion although solid with no rust jacking, looks very rough with surface rust galore. That will get dealt with in the future. Any extra insight on the exact location of the VIN on the frame?

I'm also curious of the drivetrain in this truck as it looks like it has all been completely replaced. The front and rear axle is a 6 lug so it seems those may be the original? The truck was originally built with a 305. That has been swapped to a 350. I have attached pictures but based on the tags and my research it looks like my engine is from somewhere in the 90's as from what I have found online it says most 70's and 80's blocks had a 6-8 digit code that you had to lookup to find out its particulars. It was also located on a flat data area on the front pass side block by the head. There's nothing there on mine. This one has the displacement in the casting on the rear of the driver side. Is there anything else I should look for that may show where this motor originally came from? A couple strange things I noticed are the front vacuum port had a short piece of hose in it with a screw rather than going to the PCV on the valve cover. The small lower right vacuum port was plugged with nothing going to the vacuum advance on dist. and the vacuum line going to shift module was disconnected at trans. This could all have been part of the previous owners doing while working on it. The choke on distributor was also not hooked up to anything. I have purchased an edelbrock electric choke kit for it.

From there it mates to a TH400 auto trans. Also uncommon for this application I believe. The tag on this one says 83 which I assume is the year and "FT" which when I looked that up it just says "rental truck" There is then what I assume to be a S/N I suppose of 2529. Does anyone have any info on what exactly "rental truck" refers to? I'm assuming this trans was pulled from like an old U-haul, Ryder, or Penske truck. If that's the case, I'm guessing it was well used, lol. The guy I got it from said the trans cooler lines were gone and someone had just looped them back to each other which is why he put new ones on. There is no kickdown switch ran to the connector on the side of the transmission. Ill take care of that.

Finally its mated to an NP203. Also wrong for this truck I believe. There is no front shaft in it as the headers that are on the motor are in the way of the front diff. Shaft came with the truck also. I am planning on putting a 4" suspension lift on it so that will likely not be a future issue. The shift lever in the cab is a single 4 position lever that kicks over to the right for Lo. From the research I have done this would have had a 5 position single lever with a very complicated mechanism to operate two rods. There is no linkage on the side of the T-case at all but it does look like it has two keyed parts for actuation. I have seen two lever conversions also. The front hubs on this truck look to be automatic as they just say 4X4 on them. The front output of the T-case spins freely and does not rotate when you move the truck forward or backward. Ill assume it is in 2hi even though everything I've read tells me the np203 is a full time 4WD or AWD T-Case. I have seen there are conversions that can be done but I don't know what to look for for that. Does anyone know how to determine that? The tag on the T-Case says 76. Would I be better off to try and find a 205 or 208 for it. I think that is what it likely came with... I have heard some people say the 203 is pretty bulletproof also. What say the group?

It looks like I have a T-case from the 70's, transmission from early 80's cab from mid 80's and engine from the 90's. I'm not necessarily upset by that, I just want everything to work together nicely. My biggest concern is the ability to shift the T-Case properly (assuming it functions properly). I'm slowly going through the quirks I keep finding and have been doing a lot of research on You Tube university!

Thanks for any help or insight you guys can provide!

 

[J-SQUARED]

A few more pictures attached here.

 

[Keith Seymore]

You are looking in the right spot for the (partial) VIN on the frame. There will not be a stamp up by the steering gear or motor mounts for the 1985 model year like there was for some earlier years. The one under the cab will be on the top surface of the top horizontal flange of the rail. The numbers on the side are part numbers, date stamps and supplier codes.

It will be in a partial VIN format, consisting of

FS123456

Where:

F = 1985 model year (80 =A, 81=B, etc)
S = Final assembly location (S = St Louis, F = Flint, Z=Fremont, 1 = Oshawa ,etc)
123456 = serial portion of VIN, which would (hopefully) match the last six of the VIN on SPID label, door tag and cowl.

K

 

[nvrenuf]

The 400/203 will be ‘79 or older. Technically, the 400 could be newer but the tailshaft required for the 203 is unique to that combo so it’s likely that it was all installed together.

Also, I don’t think the th400 had become the default 3spd auto yet in ‘85 so it’s unlikely that any th400 came in that truck.

 

[Grit dog]

Look up your truck on https://www.gm.com/heritage/archive/vehicle-information-kits. You will be able to tell what it originally had. Nest to know but largely inapplicable. You have a different engine, trans and t case than came with the truck.
Not a big deal as squares had a lot of interchangeability and still a good market for any sort you’d need almost. Although some hard parts will be junkyard parts like t case linkages etc.
what you do with it is dependent on your time ability budget and how you intend to use it. Assuming moderation on all fronts and local, pleasure use and not pounding down the freeway at 80mph often or long distances, I’d verify the operation of everything, either out a free spin kit in the 203 and locking hubs, or not, and send it!