Wilwood brake install 1975 dart

The only thing I’m not sure about is which rear mount option I should use because all are for 72 and older a and b bodies

Right, but you have a ‘69 Dart yes? They all use the same spindles, you’d keep your ‘75 spindles. The front vs rear mount calipers deals with the location of the sway bar end links. If you use a sway bar that uses the ‘69 sway bar end link locations you’ll need the rear mount calipers. If you use a sway bar that uses the later sway bar end link locations then you can probably use the front mount calipers.

I have the rear mount calipers on my car, it’s a ‘74.

If you’re not sure, just call DoctorDiff and tell him what you’re doing and what parts you have, he’ll set you straight.