CRT is good, John has been a great resource everytime I've called.
ProTrans, reputation speaks for itself, their transmissions are in about every serious Stock and super stocker in the country.
Tranzact is what I have in my car, no complaints. Joe has been helpful whenever I called with questions.

Or build your own, you wont save much if any money, but you will have a much better handle on how it all works.