There are a couple of other thing you will need to do for the swap you are talking about. One is that you will need to do some adjustments to the pedal assembly. The 4 spd is wider than the 3spd so the extra material on the pedal assembly where it bolts to the trans will heve to be removed. Also you might have to change the u-joint.

As bigbad... said the 3spd is a much more driveable trans.