He will need the 4speed bell housing. If He is keeping the 3 speed's transfer case the output shaft in the tranny has a differend spline than the input gear on the transfer case. No big deal just change out that gear. Several companies sell a kit that includes a new bearing,gear ,and seal. One big bennifit of keeping the 3 speed transfer case is that it has a better low range. That mated to the lower 1st gear in the 4 speed tranny makes for a really nice crawl ration. Sorry dont know the exact numbers off the top of my head but I'm sure someone will chime in on that. Just my .02 but while I had it all apart I would clean everything up and do a good inspection on everything. I would also recomend adding the transfer case brace and the tranny/ transfer return line to allow overflow to run back into the transfer case in case the seal ever goes. Iput a 78 4 speed in my 72 fj40 with the 3 speed transfer case. That along with 4:88 gears. I have been very happy with the performance.