Need some brake help, please...

[EagleChief]

I'm working on redoing my brakes. 1971 C10 longbed. Disc brakes up front, drums in the back. I tried searching before I posted, but came up empty.

The original problem started when I was replacing the pads. I had the front rotors turned, put the new pads on. When I put the new pads on, they were extremely tight on the rotor. Tight enough that I had to "tap" them on with a hammer. While driving, I could hear them rubbing the rotors. I also had a vibration/pulsation when braking after turning the rotors.

Fast forward to now - after a suspension rebuild and drop kit, determined that I needed new brake lines up front and went ahead and got new rotors as well. Got the rotors on last night. Tried putting the pads on, and they don't fit! The pads are too thick to fit over the new rotors. The rotors are for a '71 (RockAuto), the pads are for a '71 (Advance Auto) - 1.25" thick. The calipers are what was on the truck - I'm assuming original.

Any thoughts?

My first 2 thoughts: 1) pads were wrong, or 2) calipers were switched out at some point for the 1" rotors? What is that, '80 and up?

Is there a way to visually determine the difference between calipers throughout the 70's? Just something that I can look at on my calipers to know if they are original or have been replaced?