1970 dodge dart thumb dial radio?

I have a 1970 dodge dart swinger that didn't have the factory radio in it so I bought a mopar thumbwheel radio at a swamp meet and the clear plastic part of the radio doesn't fit the whole in the dash,
It is to big. Is there a difference in the a-b body radios? Any help would be great. Really want to install the factory am radio.

I believe that the B-body/C-body radios are bigger.