Hey wood,
no no no........ If you want to go Dualcases and you've gotta ditch your drivetrain anyways, then DO NOT buy a R150F transmission, get a 1986-1987 22R-TE 5-spd transmission, the R151F.
See, In order to use any kind of Crawler, you've got to use gear drive transfercases. This is standard behind the R151F as both it's tailhousing and output shaft are ready for a gear drive transfercase. The R150F V6 transmission on the otherhand, is not designed for the gear drive transfercase and you must buy a $350 adapter (P/N# 30-4GT) simply to allow gear drive transfercases to go behind it.
So what you need to do is get a bellhousing from a 1988-1995 3VZ-FE 3.0l V6 R150F transmission and bolt that to the front of a R151F transmission. Now you've got the same transmission (R-series) and its already ready for the gear drive transfercases. This will save you an extra $350 adapter that you can avoid.
And about the W56, My only question is "Why?" It's not as good as a R-transmission and the transfercase setup will be weaker (21-spline vs. 23-spline).
If you are going to do all of this work, then you are going to do it right, you're gonna use a R-transmission.
BigMike