Are those the ~12.2" rotors?
I'm looking at this kit for ~$760 with a 10% off Summit code.
https://www.summitracing.com/parts/wil-140-7144-dr
I got mine from Magnum Force when I bought the front brakes and drop spindles. The item numbers are -
1 WIL 140-11395 11" 4-Piston - Drilled/Slotted Rear Brakes $675.00
1 WIL 260-8419 Knob Style Proportioning Valve $45.00
1 WIL 330-9371 Rear Parking Brake Cables $119.95
2 RRP BCA56001Green Bearing w/ Snap Ring $70.00 EA $140.00
They were really cheap to ship to Australia and Clint was super helpful and swapped out the red calipers for black - and trusted me to ship the red ones to him later from the other side of the world!
You also need to get the bearing set too as they are not even close to the original ones, if you are going the drum park brake (which mine are). My rotors are 11" - but bigger is always better