I have a 64 C30, that came with 750-16 (duals in rear) I have been told that 215-85-16, is the equivalent size. My question is: Is there any other size that would still fit the duals, that would have a taller profile, thus better mileage?? Someone told me I could get away with 225-85-16, but I think that would just be a tad wider, but no taller.

1964 C-30 http://s1179.photobucket.com/albums/x383/autoart3/64%20one%20ton%20dually%20flatbed/