Used exhaust install question?

When you say the exhaust is from the headers back and "quite long" do you mean each side is a single piece? If this is the case the install will be fairly easy AFTER you remove your axle! It will be impossible otherwise. You need to separate the exhaust into at least 2 pieces on each side. This is generally done at the mufflers.

A picture or two would help.

Also, when you say it came of another Dart, was it the same wheelbase? Swingers/Scamps were longer than Dusters/Demons/Sports by a couple inches.