I've been thinking about converting my 70 340 Dart from a 4-speed to an automatic, I already have a small block 727, torque converter, aftermarket shifter, kick-down linkage and an automatic brake pedal assembly. Do the 4-speeds and autos use different driveshafts? Also, does the pilot bushing have to come out or can it be left in and is there anything else I would need to do or change? Thanks in advance.