The 2wd tranny has a shorter output shaft so it wont work on a 4wd. the internal gears/parts other than the output shaft however are the same. Transmissions for these trucks are an all around ball of confusion because of the different clutch systems, engines, years, I would guess there are at least 10 different fitments for what is essentially the same transmission. The differences are small and subtle but create big problems when you have to change the whole clutch mechanism to make it work for example. By far the easiest and most guaranteed solution is to rebuild your original transmission as it will fit without any headache. If you can do it yourself you can save a lot of $.