This is what I have on my '65 Fastback.
Front 215 60R14 on 14X6" Rims
Rear 235 60R14 on 14X7" Rims
No problem in the front, the rears rub if I hit a big bump or carry a few fat asses (I mean friends) in the back and hit a smaller bump.
This link is talks about the 15" rims.
http://www.vintage-mustang.com/forum...al&Number=1066
Let us know what you decide on and how it works
-JON