The old standby is a book named Golf Club Design, Fitting, Alteration, & Repair by Ralph Maltby. The 1st Edition was from Sept. 1974 and I think it made a 4th Edition in 1994.
There are quite a few good YouTube videos our there also.
It can become an obsession and if you aren't a hoarder you'll become one in a good way. 😆 Good luck!