Jimmy that is a very similar set up I had in my 55. I ended up running the 327, M21, and I am guessing it is a 4:10 in my 64 C/10, great combo but now I need to be able to stop the beast so looking at suspension and brake packages, from Scotts Hot rods and customs. All square tube front cross members and tig welded, everything made or sourced in the USA. Not cheap but you get what you pay for, many options to customize it to your needs/wants.
I just wanted to agree with you on the 327 4 speed comments, awesome set up.