I just rebuilt the rear cylinders on my '63 c20, 1 1/8" Bore. My Chevy shop manual listed .002-.004" between piston and c.wall. Don't know if older shop manuals list too. I never done drums before, I think I may have over honed 1 cylinder, I will find out. I am not retired, but I am poor and if I can try to rebuild for
$3 /wheel vs. $50-60, I'm gonna try to rebuild. Besides it way way fun too, I get to see how it all works in there. My rebuild kit didn't include 2 metal discs that were attatched to each end of spring on original w.cyl. I had to clean and reuse these things, they were filthy, I wish my rebuild kit included them with the springs, cups, and dust covers. I hope you can find just the cups Denny
