I just did a comparison of the amt versus mpc 1971-73 Mustang. The bodies about the same . Even with exhaust, they are Cherry Bomb type mufflers; should be flat like ERTL did on the 69 Eliminator Cougar. Otherwise, it is a good starting point.
Tim, great picture of the 1973 Roadrunner. Back in 1978 I tried to chase a 318 Roadrunner on I95 Bangor to Orono, ME with my 302 Torino. No dice. 99mph was all it would do. The Roadrunner got away.