For my project I decided that the 1 ton frame I had was not strong enough for me, considered the 1.5 ton, but the 137" wheelbase 4100 is the same strength as the 3800 (1 ton), the longer wheelbase 4400 would be a tad stronger, but I did not want that long a wheelbase. Decided on a 2 ton 6100 (137" wheelbase) but ended up finding a 6400 (161"), and I am glad I did, as I think I will like the about 12' bed.

For your project I would suggest you start with a frame that suits you from a bigger AD truck. 1 ton would probably be fine, and then next choice is a 4400, either original or shortened, then 2 tons come next.
I also liked the bigger fenders on the 1.5 and 2 tons as I can fit 9R22.5 tires I want to run.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-