Brian and Dad, Yep I put a Richmond 6 in my 65, I'm very happy with it thus far. Mods were not too bad, You can buy direct kit from Richmond only other thing you will need is Bell housing, Tunnel mods no too bad, only negitive was shifter to forward for my liking so also switched out shifter to 3 inch curved better position for me.
I'm running a 411 gear in car and can sure leave in second with no problem, one thing is all 6 are inherintly noisy but tolerable. Cost well not cheap, about 3400 and another 300 for bellhousing. I think I have picture of done swap somewhere and I will try to PM it to you if I can find it.
If you have anymore specfic questions and or need part #'s I can dig up for you. When you go to price you will find everyones about the same and they will have to order from Richmond and they will drop ship directly to you if you go that route.
Mark