My 1 ton has the same fenders as your truck, and the tallest tire I would try is an 8R19.5, about 32 or 33" tall

I ran a set on my truck for a while and liked them.

You may not be able to fit them on a 1/2 ton, depending on where the wheel is placed in the opening up and down, not sure if it is the same as the 1 ton. Also you won't find any 19.5 wheels to bolt to your hubs.

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
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-