here is what i know from researching and doing. I have a 90 4runner with the 3.0 (still), i changed trannies to a R151f and dual cases. not a hard swap. the r150 bell housing (from your truck)bolts up to the r151f. you'll need a 23 spline input for at least the crawler case (front case) as the r151f is a 23 spline output.
i had to dog leg the tranny shifter
to get it to clear the dash, and had to trim some floor board for the crawler case shifter to clear. bought a standard v6 bud built crossmember had the drive lines done.
what i've found for the 3.0 to 3.4 swap is that it will bolt up to the same bell housing, and engine mounts. hood clearance can be an issue. off road solutions
http://offroadsolutions.com/index/newproducts.htm has a plug and play kit for the engine swamp that make it a weekend project from what i know.
