Can't Stop 71 440 Demon

Working on a 71 Dodge Demon 440 4spd.
It has 4 piston calipers which are not rebuildable. I have been looking high and low and every parts supplier states that these are no longer available or that they can get one side but can't get the other.

My question is has anyone switched from 4 piston power brakes to single or dual and what is involved?

Sucks that car is finally running but I can't drive it cause it wont stop.
Try posting pics of what brakes you have. A while ago I was considering rebuilding a set of kelsey hayes 4 piston brakes and couldn't find any for them... I found out that mustangs of similar years used the same brakes so I looked up the parts for a mustang instead of the specific brakes and found parts no problem.