C/K Squarebody / GMT400 / P30 Cab / Chassis compatibility?

[James Collier Jr.]

WARNING: This is going to be an odd one, and a long shot / shot in the dark to boot. I hope it's not too far off topic, but there just aren't really many forums for this.

 

First things first. I currently am in possession of a pair of Pace Arrow motorhomes, one a 1982 on what I believe is a P20 chassis (6.2 diesel / 16-inch wheels), the other a 1983 on what I believe is a P30 chassis (7.4 gas, 19.5-inch wheels), though I have read this one is likely a P32, not a P30, which I believe only has minor suspension and brake differences. I am not sure which one I will use, or if I can even do what I have in mind. Both have severe roof problems and are too much work to repair properly to be worth it, but run great, and both are extremely low mileage (14k and 65k, respectively).

 

I have seen several 3500s (same cab as 1500 / 2500) with the same 19.5-inch wheel and 7.4L, with an added valance of sorts between the main grille and bumper, suggesting that the cab sits higher and is on a different frame. I have also noticed similarities in rail-to-rail measurements between the P and C/K on chassis diagrams I have downloaded. Auto Zone shows the same body mount kit for the P and C/K for 1983. I have to wonder as well if the late-model U-Haul 26-footers are on a P30/P32 chassis. Even late-model GM cutaway cabs and cab/chassis for U-Haul, small buses and even the Kodiak MDT appear to be the same Express van cab (the G-van's replacement, which was the basis for some box trucks of its vintage). I have also noticed that some of those box trucks had a longer, more raked nose, even though it was a G-van cab. A few pics are attached -- a motorhome similiar to the larger one I have, a "high-boy" 3500 box truck with the extended valance and the same 19.5-inch wheel, and the "Lil' Kenny" kit built for the late-model C/K frame.

 

All of this leads me to believe that a square-body or GMT400 C /K cab would mount on a P chassis with little fuss and muss. Which leads to my main question -- does anyone know if this can be done? Seems like it would work, but I'm hoping someone here has done this before or knows someone who has. I have run across a few similar projects, but could not confirm any of them were finished to the point of a running, driving (and safe) vehicle.

 

The reason I ask such an outlandish question -- I've had a couple ideas here. One was to simply swap a cab / nose from a 73-03 C/K onto the frame. The other idea was a "Lil' Big Rig" kit (scaled down Peterbilt / Kenworth cab built for popular full-size pickup frames). In the event anyone is inspired, the Kenworth version is built specifically for GM, and can be adapted to Dodge, while the Peterbilt version is fitted for use with Ford F-series, though either can be adapted for the other.

 

I'm thinking some modification would be necessary, as the P's steering column sits directly beside the engine. The steering box shows a different part number between the P and C/K, so I wonder if this would be the thing that makes it impossible. However, I wonder if the cab sitting lower might correct this position, or if I would need to change the column / intermediate shaft, or even the steering box itself? Any help would be greatly appreciated. I want to iron out the if's on this idea before I start tearing things apart and find out some technical snag, especially as the Lil Big RIg kits are quite pricey. Would rather have some answers before I start. Kinda thought about yanking the 7.4 and trans from the '83, starting fresh with a used U-Haul, and saving the 7.4 for when the U-Haul's 8.1 gives up. Might be easier, but I like the idea of using what I have if I can.

 

Thanks in advance for any help or advice.

Edited April 6, 2020 by James Collier Jr.

[Doug_Scott]

Did you try asking the  manufacturer of the "Lil Big RIg" kits for answers?  When you say "severe roof problems", were they run through an overpass they shouldn't have?  What are you looking to make of these vehicles?  By that I mean do you have a particular finished vehicle in mind, and you are just looking for ideas on how to get there or are you looking for ideas on what to do with these vehicles?

 

 

[James Collier Jr.]

6 hours ago, Doug_Scott said:

Did you try asking the  manufacturer of the "Lil Big RIg" kits for answers?  When you say "severe roof problems", were they run through an overpass they shouldn't have?  What are you looking to make of these vehicles?  By that I mean do you have a particular finished vehicle in mind, and you are just looking for ideas on how to get there or are you looking for ideas on what to do with these vehicles?

Long story short, carpenter ants burrowed into the roof and ceiling through a non-pressure-treated wood repair (in a hard-to-reach, hard-to-see spot) on one of the roof hatches, and it has taken about 7 years of leakage to figure out where the leak is. At this point, the ceiling and walls have soaked up 7 years of rainwater and have grown mold and mildew inside the walls. Also, the leak appears to have caused some electrical problems as well. Incredibly, both models suffer the same issue.

To fix it right, the entire rear third and some of the front will have to be gutted and rebuilt / rewired once all the leaks have been repaired ((more than one, I just outlined the major one). Simply too much work to repair it properly, could buy another motor-home cheaper, I'm just looking for a cool way I can salvage the chassis and running gear without actually pulling the engine, and swapping it to standard C/K / Kodiak cab or the LBR kit would be a good start to building something better from scratch, though it might be easier to swap this engine / trans into something else that's in better shape.

 

Lil Big Rigs has an FAQ that pretty much gives the generic 'see answer above' about adapting their kits to other chassis, and elaborate further that they do not research fitment to applications other than what it was built for, so I presume I would get pretty much the same thing if I call them. I'm hoping someone here has dropped a C/K / GMT400 cab on a P-chassis to confirm fitment, that will tell me what I need to know. I already have confirmation the mounts themselves are the same, it's a question of whether the locations and spacing are the same.

 

To clarify, I currently reside in the P30 and will need to do something in the foreseeable future, whether it is buy another RV, convert a school bus / UHaul truck, or cobble together something on the P30  or P20. I would like to salvage the chassis and running gear from the existing RV at least. So I guess you could say I'm looking for ideas, in addition to whether my existing idea would work.

Interesting post on another forum I just found that gives a little glimmer of hope this may work. Be advised, this IS from a model-maker's forum, but several contributors confirm that at on the real thing, least some of these P-trucks used a standard one-ton chassis, which I believe would be the case for an RV. One person alludes to a difference in lug pattern being the tell-tale sign.

http://www.modelcarsmag.com/forums/topic/76803-non-trucker-questions-on-chevy-p30-availability/

 

One thought about the U-Haul truck conversion I touched on as an alternate, how different is a Mark IV 7.4 from an 8.1 Vortec, apart from the fuel injection? Could the 8.1's intake bolt onto the 7.4, or does the typical splayed vs vertical intake bolt issue apply there?

Edited April 6, 2020 by James Collier Jr.

[Mike Linstead]

In the process of same situation  you find anymore  information.  I no motorhome has no cab perches but easy to put on steering box different but not hard to make work its not bad to do if you don't mind time consuming little ******. Great upgrade for my 66 c30 now 66 with 1982 p30 chassis  getting ready to build atilt bed car hauler on it