Hey Mav,
The easiest way to identify an auto tranny is by the shape of the sump pan. I would suggest going down to a REAL parts store (not Chief's or Pep Boy's or Kragen's) and ask the counter guy for an index. If nothing else you can trace the pictures in the books onto a piece of paper and take it home and compare it to what you got!
Personally, I find the TH 350 to be the easiest to find & easiest work on and the cheapest to buy parts for, The turbo 400 to be the most rugged (great pulling tranny! I have one in my '66!), the powerglide to have the most longevity, and the 700R is definately the most complex, heavy, cumbersome, finiky, and by far the most expensive pile of crap I've ever seen. (but it is one solution for better mileage as it is a true overdrive)
Hope this helps!
--The Hilander http://www.picturetrail.com/gallery/view?p=999&gid=559262&uid=458225
