Super Six install on 1974 Dart

When we were racing my wife's '73 Duster. The 2 biggest performance improvements were.

1) A TransGo shift kit.
2) installing a 2 1/2" exhaust pipe.

Those 2 modifications alone, lead to dropping almost a second off her track time. I know, because I kept detailed records of our runs. The shift kit allowed us to keep the transmission in gear longer, thus allowing the engine to rev up. The exhaust let the engine breath.