I have the four-speed in my '80 Volare. It is a really tough transmission and was used all the way up to a two-ton dump truck. It is a lot tougher and heavier than the five-speed.
You'll find the splines on the input shaft are different so it won't fit the clutch disc. If both discs are the same diameter you might get the newer one in but if the thickness is different you'll need the newer pressure plate which likely will not bolt to the flywheel.
Next is the matter of the shifter and linkage. You'll have to look at how each shifter is mounted to figure out if the new one will hit the dash and come through the floor in the right spot. The linkages may hit the existing body or cross members.
I think you'd be better off finding the right replacement. The four-speed used in my Volare had an overdrive gear installed to replace the third gear set, then the shift lever was flipped over to switch third and fourth gears. That means shifting to third gear puts the transmission in fourth and a one-to-one ratio, and shifting to fourth puts the transmission into third gear which is an overdrive ratio now. You can identify that by looking at the two shift levers on the transmission. One will be going up and one will be down. The five-speed will give you the same thing, just with one extra gear to shift through to get there.
Thursday, May 30th, 2013 AT 9:46 AM