What transmissions are compatible with a 1969 Chevy Chevelle ?

[Michael Scofield]

I'm looking to put a new transmission into my 1969 Chevy chevelle, now I dont know which transmissions are comparible with my car, its too bad the dont have like a size code or something.
Anyways, looking for a performance transmission, how do I find out if it would fit my car, or do you recommend any special Make/Brand?

I know very little about cars so please try to keep it simple for me

 

[zora]

well you didnt say automatic of manual, so a turbo 400 or a muncie 4 sp

 

[Bullcrappy]

the Power glide, th350 and even thr 200R4 are the same size and fit without changing drive shaft...