I can’t help much I am in the same boat as you trying to figure the same stuff out BUT: here is a link I found on this forum for Burgie’s 1964 C60
http://www.chevyc60.com which will be extremely similar to your project. His page describes in detail, with where to get parts and how to rebuild the Hydraboost. I will definitely subscribe and follow you along, and if I make any headway on my 1963 C50 I will post on my build page.
http://www.chevyc60.com/