01 1973 and later 904 transmissions are the best for performance builds, but they're also more difficult to find since many were the undesirable lockup styles. To make things easier, we got a race prepped case from A&A Transmission, which offers several advantages over a stock case. The case is completely cleaned and glass beaded, and offers improved lubrication and venting as well as a machined provision allowing for line-pressure adjustment from outside the transmission. Additionally, the bell-housing portion is cut out for easy access of torque converter bolts. For the money, this case gives some great advantages when starting your transmission build.