A&A Transmissions at
http://www.aandatrans.com sells good quality parts for 727. They sell in the kit and piecemeal as well, which is nice. Another nice thing about them is when you order a kit or package you get EVERYTHING you expected. Sometimes you don't. For instance, I ordered a no name 727 MASTER REBUILD KIT from my local speed shop and the POS came WITHOUT BANDS. I went to the counter guy what kind of F***ing rebuild kit comes without bands?
Anyhow, A&A is really good in that respect, and they sell a few things that are hard to find like that bolt in sprag ($100), master bushing kit (many at home guys don't change these cause it's hard to do without the correct tools), selective kits (snap rings, thrust washers, etc. these are a must cause you almost never have the right thickness to get good clearance.
I've also heard really good things about the TransGo kits and valve body reprogrammers (one of those upgrades that might be a good idea). And I've heard a 5-clutch front drum is a good upgrade (although you will get varying opinions on this). TCI sells a special pressure plate for this application, although if you have access to a machine shop I would recommend just milling the plate yourself (it's all they do, and it was a sloppy job at that).
Hope this is a good start. Sorry so wordy..
P.S. One thing about A&A.. If you are in a big hurry, keep on top of them. They tend to lag just a bit if you don't give them a friendly reminder here and there.