Brake Caliper Identification - Need an Expert Eye

[c6_rob]

I picked up a rear end for my 52 3100 that originally came off a 77 El Camino.

The rear is great and came with disk conversion. The problem is that I cant ID the calipers. Im having trouble figuring out which car they came off of. I originally though 79 Trans am but when I looked at the rebuild kit it the seals were too big.

The piston bore is about 1.8" to 1.9"
The rotor is about 10.5" and vented

Attached are some photos of the calipers





Thanks