Welcome to CHR:

I love the 66 Mustang - one of the nicest looking ever made in my opinion. There are a lot of Ford guys here (I'm really a Chevy guy when it comes to hot rods) - drive Fords and build the Chevy.

Not to bust your chops, but have you thought about upgrading to a modern 5 speed? This site will walk you you through all the components necessary for a successful swap:

Modern Driveline - Classic Mustang Small Block T5 conversion parts kit 1965-1973

Yes, it's an investment but you have a new, well designed transmission and don't have to mess with 50 year old parts that have been through who-knows-what. I have a Super T-10 in a '63 Nova from a Z-28. The day it breaks a T5/T6 will replace it.

Good to have you with us. Others will chime in I'm sure.

Glenn