Your trucks, your decision.

I personally would keep a 4-71 in a truck that came with one, and or upgrade to a 4-71T, not a 53 series.

19.5" tires under a 650 cab and fenders will look very much on the small side, not something I'd do.

•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-