the 2RZ and 3RZ are the same motor from the deck up. The difference is the deck height itself, 2RZ is shorter, and has more of a car-like stroke for 2WD trucks. 3RZ is deeper, has a stoke comparable to the early 22R's deeper stroke, and will have greater compression - but will drive more tractor-like. The 3RZ-FE is a 2.7-liter inline four-cylinder gasoline engine produced by Toyota from 1994 to 2004. It was a replacement for the well-known 22R-E and used mostly in commercial trucks and four- wheel drive vehicles such as Toyota Tacoma, T100, Land Cruiser Prado, 4Runner.
A 3rz/2rz bellhousing will bolt right up to the W or G series trans found on most 4cyl trucks. If you have a 3.0 v6 it is far easier to do a 3.4 swap as it bolts right up to the R series trans and as far as I know uses the factory motor mounts. The 3.4 swap normally requires slight hood clearancing without a body lift.