8.25" rear axle and disc brakes???

Guess I didn't explain my question enough..I know WHAT a core is, what I want to know is WHERE will the core come from?

A bodies never came with disc brakes in the rear, so what vehicle do I need to tear a set off from to turn in for core? Year? Model? :dontknow:

For that price, I'll rebuild what I have. Ceramic shoes, nitrogen wash the drums and have money to spare.