The 46RH is 13" longer than the TF999. That, my friend is a big deal on a short wheel base Jeep. The 46RH is what I am currently running in my Jeep with a 5.2 swap. I pushed the engine as close to the radiator as possible and stretched the wheel base to make it work. I am currently shopping for an old 727 so I can get some more drive shaft length. My YJ drive shaft is about 16" so I'm thinking a 3" drive shaft may be an issue.
87YJ 5.2/46RH/NP231 D44/9in 4.56 4 link rear, radius arm front
My Build http://www.jeepforum.com/forum/f22/daddyjeep-121-day-87-yj-5-2-lcg-4-link-build-1479204/
Start planning for 2014, updated site http://www.bantamjeepfestival.com/