Well, aside from the bell-housing pattern not being the same between the 3.0 and the 4.0 engines, there is another issue...
I converted my 1987 to a 4.0 and I had already been running an '88-91 2.9 M5OD-R1, and as you may have already read the 2.9 has the same bell-housing pattern as the 4.0
so I kept running the 2.9 trans, which worked fine for about two years until the 4.0 engine literally twisted the output-shaft off in the T-case input.
In the case of the 1993 I'm about to swap, I already have an 4.0 M5OD-R1HD
to put in the 1993 when it goes back together.
People who know me well are generally aware I am a parts scrounger/packrat
who usually has enough parts on-hand to build an entire truck from parts
(I actually have a spare FRAME and a spare Cab for my gen1)
And as a note that's why I have to get the 1993 running, so I have something to drive while I replace the cab on my 1987 Supercab.
You will need some things like a radiator, radiator hoses and throttle cable,
but the motor mounts are the same...