I'm sure many have had good luck with a rebuild kit, but on a single circuit with a car as nice as yours, personally I'd get a whole new MC. As old as yours looks from the outside, you may have pitting and corrosion in the bore. Don't chance it.

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63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6