The '57 1/2 through 1 1/2 tons used the 265 (also base v8 in cars), the 283 was used in 2 ton and larger.
There is one issue with restoring it, and that is the fact that the p/o already started to cut it up. Going back to original will most likely require getting an entire replacement chassis. You could go for a comprimise, use the updated suspension, brakes, etc, with a period dressed engine and steel wheels to get an original type look with modern handling and performance.
