Longer wheel studs?

I am going to guess this is your problem. The car has 10" factory brakes and the new wheels are shaped wrong to clear the drums (too small on the back side) so they are riding on the drums. Same thing with the caliper but with the caliper off the car the 10" rotor is about 2 inches behind the hub instead of flat at the 10" diameter against the wheel like the rear so it will clear. The 70 a body also has bells on the drums from the factory unless they have been replaced.