The T5 transmission is arguably not big enough for a 3/4 or 1 ton truck, they came in an S-10 pickup.

I also switched from 5.14 to 4.10 and 8r19.5 tires in my 1 ton, with original 228 GMC. It does very well, and we live in the mountains.
4.56 is some improvement, but better to hold out for the 4.10.
I bet the 216 with 4.10 gears in flat Florida works out great.

•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-