1st and 4th have different ratios for sure, so you will need to use the gears from the 2wd mainshaft onto the 4wd mainshaft. and use the 2wd countershaft/cluster gear. I was going to do the same for a friend, but the donor 2wd trans was in bad a shap as the 4x4 unit he had. ended up using my parts trans I just bought a week before and built it instead. but it can be done. as long as your mainshaft and housing are still good, and the gears on the 2wd are still good. you will not have as low a first gear as with a 4x4 though.
