Depending on hp you should look for an Audi 01E. That is the highest rated 2wd Audi box and handles 450 BHP and similar torque.
01X is your second best option and should be good for 300+ BHP. I actually learned alot at the
www.gt40s.com forum. There are some genuine gearbox experts over there.
Regards
Jackal
P.S. I was told to stay way clear of 012 boxes. I bought my 01E from England on Ebay. It was from Prestige motors. They break all the big Audis. S8's, A8, S8 etc. etc. You will come right there.