As for the transmission question, any 4 speed you get will have a 1:1 fourth gear. Some may have a better mix of gear ratios leading up to the 1:1 final gear (and some may be worse) but since you already have the open driveshaft rear end, I'd consider a T5 (five speed) transmission. Any four speed will not improve anything but the rpm drop between shifts and it will give you a synchronized 1st gear. You will still have the same top speed and your engine will still be turning over at the exact same rpms as it will with the 3 speed. Good luck!
