My 97' has 123K and the transmission (automatic) is starting to slip more and more every day. I am thinking on rebuilding the transmission...o is it better to just get a new one? (I just want a stock automatic).
Make the minor modifications to a 4R70W auto out of an 01 Mustang that is needed. You can find these for around $500 - $650, you cannot rebuild a 4R70W that cheaply. If you do decide to rebuild it, rebuild it to at least 98 specs.
The modifications needed to run the newer tranny in your car is that you re-use your tranny sensors from your 97, you need to re-pin a connector and you will need either a Speedcal or different speedo gear, depending on what rear gears you have to keep the speedo and odometer correct.