Frame/chassis swap questions

[slotard]

I have a '73 C20 Camper Special. One of the things I really like about it is that here in CA, there's no smog testing (or any other sort of inspection) required for trucks '75 or older. Seeing as VIN is body rather than frame, a swap shouldn't change that.

If all goes well I'll be coming across some money before too long. Right now I have 350/350 with way too big of a carb (Edelbrock 750), 4.10 rear end, atrocious mileage, and not a great cruising speed on the freeway.

I'm thinking of looking for a damaged (body only) 99+ 3/4 or 1 ton, and swapping my cab/bed over, keeping the modern engine/tranny/suspension. Probably gas rather than diesel, unless I find the right deal on a DMAX. Obviously I'll have some electrical fun, I'm expecting that.

My question is whether it's a reasonable swap when it comes to the frame. Do things fit reasonably? I'm seeing a 1.5" difference in wheelbase (the new trucks are longer), that doesn't seem like a big problem. I suspect modern suspension geometry is better, rear discs rather than drums, etc which is why I'm considering it.

Thanks for any help. If I don't, I certainly need to find a smaller carb... probably 500ish. That would help with mileage, but not cruising speed.