1984 GSL-SE Caliper Questions

[magpiemini]

First, both the front and rear rotors are single piston, one side, YUCK, even the old English cars used at least two pistons. Any suggestions for better calipers?

Second, I was able to open up the front caliper wide enough for new pads but the rear caliper was a problem. I could not press the piston back, they do work so I know they are not stuck. I could not use new pads, had to put the old pads back in for now.

Is there a trick or special tool for those rear calipers?