12-14k load is maxed out or overloaded. The truck is rated for 16 and weighs 4K or a little more. The 235 is a good engine but not overly powerful.
Therefore not much need for faster gears, you'll never use them... Unless being foolish on a downhill.
I estimate the slow gears you have will be necessary.

Be sure brakes are in excellent shape, may consider a dual circuit master cylinder but otherwise original should be just fine. Try to keep total weight under 16k


•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-