Nick, I was recently in the same situation with the clutch slave. Mine was in bad shape inside and out. Taking price into consideration, I elected to buy a new Hye-dra-cyl stainless unit from Moss, rather than rebuild the old unit.
As for the the clutch and brake masters, and brake booster - there was no doubt mine needed rebuilding so I shipped them to White Post for sleeving and rebuilding. Not cheap, but worth it to me!
My old clutch slave:
New stainless clutch slave:
A recent, informative thread on clutch slaves, if you haven’t seen it yet: