I just bought a 3800 and I believe the tire said it was a 7.5x17, I might have that backwards. I'll check tomorrow when I'm by the truck. If it does have 17s, those are easy to find tires for. As well as rims.
1954 Chevy 3800 Long Bed: ex-fire truck turned farmer's town run about turned 353T powered retirement project 1953 Chevy 6400: the work truck