Hello To all: I am trying to fgure out how to tell the size of a rim. One set came off my 70 and are originally 69 rims so I am guessing they are 14inch. The other set I bought and are magnum 500 rims, not sure they are size the box states since they are used.

Measure the inside of the wheel where the bead locks on the rim. It should be just under 14 inches if it's a fourteen inch wheel. If it's just under 15 inches then it's a fifteen inch wheel. I have the fifteen inch Magum 500s on my 1970 Mach1. They weren't an option for the 70 but they sure look good on them.