I just received a rebuild kit and other related parts that I'll use to rebuild the M20 4 speed in my 66 GTO, I bought everything from Paul Cangialosi at Super661. I've been watching Paul's videos on how he builds his transmissions, he calls these videos the muncie tapes, I believe there are 4 of them. Anyways, very informative and cool to watch, I thought I'd pass this along, in case someone else is doing a 4 speed rebuild. I'd post a link if I were more computer literate, but the videos will show up on a google search.