You don't need an r154 bellhousing to put a w58 on a JZ motor. Actually, the r154 bellhousing won't fit the w58. To put a W58 behind any JZ motor you just need to go to the toyota dealer and buy a MKIV supra non-turbo bellhousing. That car had a 2JZGE with a W58 behind it. You'd also need a flywheel and clutch from that car.
If you wanted the stronger R154 transmission, you'd need toeither buy one from a JDM JZA70 supra or buy one from a USDM 7M supra and swap the bellhousing and flywheel for the ones from a JDM JZA70 (came with the 1JZGTE engine with and R154 behind it). You can buy that bellhousing and flywheel brand new from several places online.
As far as automatics go... you can buy a JDM 2JZ automatic trans online for a couple hundred bucks. Poeple who buy 2JZ motors usually get a "free" automatic tranny with them and sell it cause they don't want it. You'd also need a 2JZ automatic trans flexplate, which, if you're lucky, will come with the trans.
I'd stick with a 5 speed.