I know that between the 258 and 304 the transmission options typically interchange for manual gearboxes. As for autos, the Chrysler A-904 and A-998 were not an option behind V block engines but they might have been in much earlier designs of my car. Not sure if there was an issue that carried over with the Jeeps too. I think the A-727 and A-999 were okay but I don't know about that last one since the ID sounds pretty strong considering the mess of things at that time. You'll typically see 4 and 5 speed manual gear boxes of the Borg Warner variety but I think Aisin Warner took over during the 4.0L period.
You might be able to use an AX-15 if you ever find one. If you find an SR-4, junk. Other than that, I think you should be able to keep axles and push 65 on the freeway pretty easy. If you're concerned about overdrive I would suggest swapping out differential gears for something higher or only using 5 speed manual transmissions. You're just not going to find a 4 speed auto for this thing without a lot of work. It might still exist in some Dodge with the A-512 or 42RH tag or something like that but I'm part of the group that doesn't consider the 700R4 an option and I don't know anything about the TH400 to help with those either.