Oh my! After taking the last few days to read through
all the posts in that link, I think I'm suffering from a bit of
vapor lock of the brain! 
LOL The whole thing has my head spinning. A440, A450, FZ62, BD240, IHC345,... my pea brain is still smoldering from the code numbers for all these trannies/t-cases! Maybe if I knew what they came from and their configuration I'd understand it all better.

(Then again, the last time I was seriously into swapping and stuff the 700R4 was a fairly new trans.

)
I came away with a decision (of sorts) and a couple of questions. Hopefully this will help 4bt4toy answer his questions too. If not, please excuse the hijack. :emb:
Through it all I have decided upon the 4bt2t motor. Mainly because of it being an IDI (indiredt injection) that it is better for use on WVO (to my understanding, please correct me if I'm wrong). I will be running mine on homebrew BioDiesel, so this appeals to me. I may incorporate a WVO kit so I can go either way. That way on a road trip, I really don't have to go back to dino Diesel or haul a bunch of extra fuel with me to get home.
The
question I have is this; what's the big deal about using the auto tranny that comes from Izuzu in these trucks? My thinking is that the biggest thing is to mate it to a t-case. I'm sure they are durable enough otherwise. If they're built to last 300k miles in a loaded truck weighing in at 15-25k lbs, it should last until my grandchildren get my truck! My Scout is gonna run at about 5k lbs most of the time, unless I'm towing something. The idea of the Diesel swap for me is dependable long life with great fuel effeciency and flexibility.
So, how hard could it be to adapt a t-case to it that works with the application you are running, to whatever auto comes or can go behind the engine you buy? It seemed (to me anyway), that in that link there were some swaps that would be using two adapters to bolt the trans and engine together, then another for the t-case. Is it really that difficult? Or are people willing to do just about anything to run something they know or trust? What am I missing here?