Wow, you need to find some new parts sources.
Rock Auto has calipers for around $25 each, rotors for around $50 each. If you currently have disc brakes, you would need to find the caliper adapter off a post '76 big car, like St Regis or Cordoba, to allow an upgrade from 10.87 to 11.75 rotors.
Other option is a Wilwood set up using the same 11.75 rotors with custom adapters $125, and Wilwood Dynalites @ $125 each. Pads are another $50 and you have four piston, lightweight calipers on the biggest factory rotors that will fit in a 15" wheel.
Another route is a custom Wilwood kit using aluminum hubs, 12.19 rotors and their forged aluminum calipers for the absolute biggest set up that will fit in a 15" wheel. Expect to spend around a couple grand for this kit.
If your running 17" wheels, then kit options are almost limitless and offered all over then. Expect prices to start around $1500 and go up from there.