We need more info from you to be able to make informed suggestions.
What engine?
What transmission?
Rear axle gears?
Tire size?
Weight of truck empty?

What transmission and or rear axle gears do you have available to swap, if any?

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-