Actually, any of the gas caps from any of the previous years will fit, except the specialty pop open caps from the "concave taillight" panel years (67 through 69). Actually, I am using a 71 Mach 1 cap on my 65 X-tremestand as I think it was one of the nicest caps ever made for the vintage Mustang....
That I'm not too sure about. I'm not too familiar with the rear tail panel moulding of the 71-73's. The 67-68 won't work, because the tail panel isn't flat but concave, or is it convex? I could never keep the difference straight.....
the 70 mach1 caps works perfect on my 66. The fit is very good. There's no gap around the cap.
Member: Slightly Modified
66 coupe 302
66 fastback 351W