Since I could not sleep well last night (between gear ratios, adapter plates ideas, Toyota 5 and 6 speed auto tranny and wait for it... GM 6L80E).
Here comes the wishful thinking.
Did some internet research and came up with nothing regarding swapping a Toyota 5/6 speed into our FZJ. No adapter plates, no bell housing, none of that.
I did stumble upon the GM 6 speed tranny in one post here, in which a member swapped an entire GM powerplant (yes it's been done before, but never really paid much attention to those threads, because I am not really interested in having a total swap... I got a 20k miles or so freshly rebuilt 1FZ-FE, so there is no point at this time to get a V8).
Apparently other people have done some early R&D regarding the GM v8 and 6L80E swaps.
Some have come up with a V8 to Toyota transmission adapter plate, others with a 6L80E to transfer case adapter.
Here comes the wishful thinking part:
Would the symmetry be kept in a mirror image when using the V8 to Toyota 4 speed adapter plate?
In other words could that adapter plate work on a 1FZ-FE and a 6L80E since the bolt pattern is the same, but on the opposite sides of the plate?
Then there is also a 6L80E to Toyota transfer case adapter plate. So that's good as it is.
Both of those plate are apparently expensive. Only madness would justify the swap at this point. The cost of the transmission, engine to tranny adapter plate, tranny to transfer case adapter plate, TCU, programming and labor maybe.
Here is the V8 to Toyota 4 speed adapter plate:
712535-D : Land Cruiser FJ80 & 100 Automatic to1986 & later V8 Engines | Advance Adapters
and the 6L80E to Toyota transfer case adapter:
6L80E to LandCruiser 4-speed auto HF2A transfer case
It is possible these parts could be found a little cheaper, but what does a few hundred dollars less do in this scenario? Not much.
I hope someone can chime in regarding the mirror image symmetry regarding the engine-transmission plate bolt pattern. I have no idea.
Of course there is the length of the entire setup to consider too, the new tranny, and both plates.