Well, first off, welding the housing could probably be done to repair it, but you would need to disassemble the tranny to drill and tap it. The 2WD tranny is the same as the 4WD tranny except for the tail shaft and tail housing. To run the 4WD tranny, you would also need a transfer case behind it with the 4WD rear drive shaft. Otherwise you would have to disassemble both transmissions and swap the parts over. So if you get the 4WD tranny, might as well get a transfer case to put on the back and call it good. Who knows you might want to finish that up and have 4WD