Hy panman, according to my brake book there are four different possibilities for master cylinders for a 1982 C10, all of them have a bore of 1.125" or larger so they would work. A few years ago I did a conversion for a guy from single system to dual, his one ton had the 14" rear drums, he did all the research I just did the install. He has toured the truck around North America with no problems. I'm not an engineer, just a mechanic, and I don't second guess an engineers design, unless that design keeps failing, that's why I suggest not going smaller than the original master cylinders bore, hope that helps.
