So here are my plans for the 68 Dart low mileage four door wife's car so far.

What do you have in mind for brakes? OE 5x4.5 will widen the track making wheel selection thin 67-69 Darts have less room than Barracuda, Duster, Demon, and Dart Sports so your going to need a wheel with positive offset if you want to run anything wider than 6" and have it not rub.

Dr. Diff is the go to for brakes.