3/4 Ton (Dana 60) Disc Brakes

[Gimme Jimmy]

I am working on a way to retrofit disc brakes on my '71 3/4 ton GMC LWB. I have a pair of 13" x 1" thick ventilated, slotted rotors that are a perfect fit on the back side of the hub. The vertical space between the brake flange and the backs of the rotors measures 15/16".
I am currently not sure what application they were intended for, but they look like a good start. Does anybody have any good ideas about what calipers would work best? I can fabricate brackets to mount the calipers. Any suggestions will be appreciated.