Great story, thanks for sharing. Regarding the tires, I don't think there is an easy axle replacement. I had 22.5 wheels for my '50 COE altered to fit the original axles (pretty expensive and now hard to find someone who will do this). With 9R22.5 tires the diameter of the tires is the same as 8.25x20. For the use of your truck I would suggest sticking with the 8.25x20 bias tires. They last longer, have tougher side walls and it doesn't sound like this will be a highway or daily driver. Regarding the gross vehicle weight, my COE is considered a 2 ton and the GVW plate says 16,000 lbs, so yours looks to be a ton and a half. That is what they call nominal rating which is below what you can actually carry. Regarding cab size, you are correct, same cab. Regarding cab corners; this is a very common problem and many vendors carry patch panels, such as Jim Carter and the Filling Station.
Kent


1937 Chevy 1/2 ton
1942 Chevy 1/2 ton
1947 Diamond T Model 509
1951 Chevy 1/2 ton
1950 Chevy COE Model 5700 ~ "Barney" ~ And more pix