67 Dart GT Rearend Question

Look at the back of the axle from behind the car. Do you see a cover with bolts that go around to bolt it on? If so, it's probably a 7.25" axle. If it's smooth looking from the back, with no bolts, it's an 8.75. I would guess that your car has a 7.25, but you never know for sure. Who the heck knows what's happened in 40+ years, too. It could have a Chevy axle in it for all we know.