Hi Chris, here are 2 part numbers for the rebuild kit for your HUP's master cylinder. UAP part # NUP33, or wagner part # F3630. They are very simple to rebuild and it probably just needs to be honed ( sp?) out and the new rubbers, etc... installed.
If yours is too badly pitted, I know I have a couple spares kicking around that would probably clean up OK for a rebuild.
Jeff
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