I'm new to the whole "lets change stuff on a car" thing. I bought a 67 Bel Air. It has a chevy powerglide transmission in it. I am wanting to change it to a 3 speed or 4 speed. I do not know how to go about finding out what transmissions will mount up or anything. Any advice is appreciated.

Things I am wanting to do...
Disc brakes instead of drum brakes
Transmission
Engine rebuild (never been done)
Reupholster
New seals for the doors and trunk
Paint
Clean out the rear end

Basically I plan on making this car as new as I can without taking from the original look. I'm going back to the same color black and getting as close as I can to the same upholstery.

Thanks for all the help.

Have you considered sourcing a donor vehicle, and doing a drivetrain swap? Find a nice roadmaster or something (LT1, Just shy of 300 HP) and you have just about all of the parts you would need. Not even counting the modern engine/fuel injection options that would open up.

I don't pretend to be an expert on this subject by any means, but if I had to do it, that is the route I would go.

pretty much all the chevy 8'* had the same bolt pattern. i dont know about the six. i would start with the engine because what you go with there will kind of determine what you want to do with the trans. like he said you could go with a whole setup from something modern, i think if i was going to do that it would be a ls engine with the t56 six speed you can get them as whole peices or find a wrecked one, you would need a whole bunch more than just the engine and trans.

or you could go with a old sbc, you can get a crate engine for pretty cheap and a muncie 4spd. not a whole lot of wiring and that sort of thing to get it going.