I have a 73 swinger with a 318 in it and what I believe are stock disk brakes on the front, I assume the caliper is as well...has one big piston. I ran out to NAPA and bought some new rotors and pads, but had a hell of a time getting the caliper back on. I put a C clamp on the piston to pull it back and It seemed like it was squeezed all the way before i was barely able to slide the caliper on. I took the C clamp off and finished working it into place but now the wheel doesnt spin, like the brakes are engaged. The piston seemed to be working fine when i tested it while it was apart, came out maybe a quarter inch. The only difference between this new rotor is that both sides of the disk are the same width, where as the old one had one disc half the size of the other, like it had been turned down on just one side. Both passenger and Driver side were like this. I also put the skinny little vibration pad with the adhesive on one side that came with the new pads...was that a nono?
I'm afraid to pump the breaks incase it tightens up even further and i'm not able to even get the caliper off, but i'm not sure why its so tight...any idea's?

 

First thing I'd suspect is "junk in the caliper" that is, garbage/ rust towards the bottom of the caliper that won't allow the piston to fully return.

But these days, with all the Chineseo junk parts, I'd also not discount that you either got the wrong or incorrectly made rotors

Unfortunately (I used to turn rotors and drums) while the MINIMUM rotor thickness is easy to discover, I'm not sure how you'd find out the "new" rotor dimension.

 

Some brands of brake pads are just plain thicker than others.
In one case Hawk brake pads produces two different pad for the same vehicle with two different part numbers. Only difference is the thickness.
Take one of your new pads to the auotparts store and check against another brand.