I think 3.42 will be much too fast for the power you have.

My feeling is the originalish stovebolt 6 might could pull 3.73 gears in a 1 ton but would sacrifice hauling ability. Obviously you could get along better in the flat land than in the mountains. 4.10 seems about right for actually using/working the truck. Mine is quite happy with 4.10 and only occasionally do I wish they were faster gears.

Are you sure you have 4.10 gears and not 4.56 or worse?

•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-