The easiest fix is to replace the caliper with a quality rebuilt, but it is possible to rebuild the caliper itself. I haven't done it, however, since the cost for a new caliper for my 78 was only $60 each. I figured by the time I'd paid for the rebuild kit, taken the caliper off, figured out what needed to be replaced, put it back together and then remounted it on the car I'd have spent at least twice that in cash and frustration.

The piston seal on one of my rear calipers went and I replaced both, just to be sure.