1975 Dart 318 (sorry but it's a4 door) Just want to say THANKS in advance the help!!

Welcome, and nothing wrong with 4-doors :) . Headers are a pain, but they go in. Car has to be high off the ground (make sure it's safe). Raise the engine up by loosening the motor mounts, and use a jack with a board on the oil pan. You'll need to drop the steering linkage, but it will all make sense as you go....
Be a great car to enter in the 318 race :D