http://www.offroadsolutions.com/products/engine_upgrades.htm#3.4l_swap_kits
It can be done. Just a little spendy. Read their technical article, its got some good info there too. ORS has a plug and play harness, he needs a new tranny, motor mounts, hood clearance (body lift works well), clutch if its a 5 speed, etc. Finding the 5 speed 3.4 was my biggest problem. Converting the auto 3.4 to manual isnt too bad mechanically so long as you get one with a crank that will take a pilot bearing, its just tracking down the 3.4 manual harness you need.
I ALMOST went this route with a 3.0 5 speed 4Runner I have that was going to get a 22RE instead. Then, I almost went this way.
3.4 will bolt to my 3.0 tranny and motor mounts, shares a lot of the engine components, plug and play wiring with the ORS harness.
22RE needs new motor mounts and 22RE tranny swap (have all this from that 90 I got from you, haha), along with all the engine components and engine wiring done custom. Only thing keeping me from doing the 3.4 is the cost and finding a 5 speed motor with wiring and ECU really.
Now Im not sure what Im gonna do with it. It still sits, 22RE is fully ready to be put together after machining and full rebuild kit bought. Oh well...
~T.J.