Allright, M5OD stuff:
The bellhousing is cast into the transmission, they don't swap. Each case must be used with it's corresponding engine.
I4 2.3L/2.5L, 2000 and older - own unique pattern
I4 2.3L, 2001 and newer - own unique pattern*
V6 3.0L - own unique pattern
V6 2.9L/4.0L - own unique pattern
*however it's reported that you can use this transmission with the whole duratec engine family, including V6's.
BUT, luckily, the internals are almost exactly the same. 4.0L engines uses a closer ratio gear set, this can be swapped into other housings, as can the wide ratio set be swapped into the 4.0L trans case.
All you would need to convert any M5OD into 4wd should be the rear output shaft, and the rear extension housing for the t-case. Those pieces are reportedly all the same. And I hope they are because I'm putting donor 4.0L M5OD parts into a pre 2000 I4 M5OD.
There is an "HD" version on some newer 4.0L equipped trucks. Everything I have heard is that these are merely upgraded synchro's on 4th/5th gear or something like that. They're not any heavier duty than any other M5OD.
http://www.therangerstation.com/tech_library/ManualTransmission.html
Manual 1354'as are rare, and $$$. Electric 1354's are common and a dime a dozen. Many people are removing the motor and finding ways to shift them manually via cable. Manual 1350's are also a dime a dozen, but require a special front output yoke unless you do other, $$$, modifications. Don't bother with an electric 1350 unless it's free and for parts.
http://www.therangerstation.com/tech_library/TransferCases.html
I have researched this extensively. I have actually made part purchases and just need the time to stick the case in, but I'm doing a clutch too, so that adds to the weekend. Stupid truck is just too damn useful!, can't have it down for long.