Front To Rear Disc Brakes

The calipers for the front brakes have a much greater clamping pressure than rear calipers do at any given fluid pressure. So no, they won't work for the rear. The rotors are usually different also.

eeeeeeeeeeeeeeeeeeeeeeeeeeeeehhhhhhhhhhhhhhhhhhhhhh whut?

For a limited time similar or same calipers to the 73 / later ones WERE used on the rear.

I run a Versailles (Lincoln) rear axle in mine, so 4x disc brakes.