Hotrod
Not sticking with the original dif has a 3.83 8 bolt pattern
So no not going to be dealing with 4.56:1 problem so no don’t need to use an OD trans.
Depends what you call expensive small number of thousands or tens of thousands

99% sure I’m using the 250 and it will get fuel injected, so it’s just what trans to use,
I don’t have any fuel, brake or electrical system now so have to build them any way
But that is a valid concern.
The hard part for me mounting the engine wise is figuring out how I want it to sit in the frame
Making the mounts is probably a 2 day job.
Also have to figure out how to get AC , have to get new drive line,
There are some merits to sticking with the short shaft out of the trans and carrier bearing set up.

Going for reliability and drive ability done right it will be the last pickup I will own