Hy pipeliner78, I've done some more research, and I think what you have is the General Motors rear brake setup. Parts I have found are
upper rear wheel cylinder o.e.m. 5464135, Raybestos p/n WC37159, $29.79 at Rock Auto
lower rear wheel cylinder o.e.m. 5464136, Raybestos p/n WC37160. $29.79 at Rock Auto
rear brake shoes Raybestos p/n 442PG $204.89 at Rock Auto, hope that helps, if you need more parts, just list what you need.
