If your budget allows, the GM 2004R with the mopar adapter bell housing is one that requires the least amount of surgery. (one of the smallest OD transmissions)
It does however pretty much require beefing the trans up to live behind a 5.9.
Next best choice in my opinion would be the A500 out of a 95 and down Dakota.
This one is a direct bolt up to a 5.9
It small enough around to not need a lot of floor cutting and handles the 5.9 pretty good without major mods.
I have this one in my Dart with a mild 5.9, but was able to do all of it myself.
Cost me about 300 including the trans, converter, large U joint yoke, and a stage 2 Transgo shift kit.
Then if you have a lot more money than time and ability, you can go with a Gear venders OD.
It is a bolt on add on for a 904, but whew is it pricey.
You also have to shorten the driveline, but you will with any of the other choices also.