i saw on a website that Cougar, Comet, Falcon, Maverick and Mustang have a ton of interchangable parts. suspension brakes steering rear end stuff like that

A lot of Fairlane parts interchange as well with the other unibody cars. But it's not a huge list. You can always go to rockauto.com, look up the part for your car, then look at the part to car list to see what else it fits.

You didn't actually ask a question so it's hard to say where you were going with this.