BP63C60,
I don't know any info (currently) on doing such a conversion.
However, I did come across this web page that applies to overhauling your
'63 C60 Hydrovac.
The company noted in the web page still has an active web site and seems to still offer remanufacturing services. If you click the "Contact Us" link it provides an email address and phone number to reach out.
The article even indicates the original GM# 3874183 (Bendix 2501847) standard C60 Hydrovac part number. If you have the Heavy Duty Hydrovac, GM# 3874184 (Bendix 2501850) applies.
Dan
NOTE: You might get a better response to your question in the
Big Bolts forum.