So, I did a 3FE swap on my 60 and probably have all of my hand notes around somewhere. Honestly, it's not that hard, but it will be time consuming and cost a lot more than it seems it should up front. You still have a very analog engine mating to an analog chassis so you just have to dig through the harness and get stuff hooked up. That said, many say the "2FE" is the engine Toyota should have built and love the performance of a 2FE. Do beware though, the 2F block is a 4 bolt main and are known to break crankshafts (as is the 3FE block).
I suggest reading through my write up. Most of the work aside from the mechanical will be the same...
80 Series 3FE Conversion Write-Up I'm in the middle of a 3FE conversion on my 85 FJ60 and figured I would add my part to the world of LC knowledge. I only have weekends to work on this so info will come about accordingly. Some background... I drove my truck from IL to CA and probably over...
forum.ih8mud.com
Now, for the curve ball. Have you looked into a 1FZ? You will not be able to retain your H55f. unless they finally come out with an adapter (someone is working on that... Wits end?) or you cut a 1FZ and your existing bell housing in half and weld them together (folks have actually done this). You would either need use the A440 auto presumably with the AWD t-case it comes with, or adapt your part time t-case which has certainly been done, but you will end up with an engine that is waaaaaaaaaaaaay more powerful, uses waaaaaaaaaaaay less fuel, and has parts availability much better than the 2F or 3FE.
The electrical side will be about the same difficulty.
All options will require exhaust work including 2 new cats which could be $750 or up to the usual $1000-$1200 if you get a whole new custom exhaust.
You will want to install an FJ62 gas tank or other tank meant for a fuel injected vehicle. There will be lots of incidentals like adding fuse blocks, fuel lines, shtuff like that.
I always had a goal of keeping my 60 not just all Toyota but also more to the original land cruiser in spirit so I was determined to stick with a Toyota straight 6. If I had it to do all over again, I would have done the 1FZ swap though, it is an engine that is like 20 years ahead of the 2F/3FE in technology and performance.
Frank