It's only difficult if you haven't done it before. I have countless problems with my Torqueflite automatic suddenly blowing up on me in places where it gets potentially deadly. I'm glad Chrysler never made manuals or that would probably try to kill me too. I want to suggest a Borg Warner T-5 but you'll never find one. If you do, it's probably going to be from a Comanche or Mustang and those don't have the 4WD housing that we need in our Eagles. I want one really badly but I don't think it's ever going to happen. :/
The Aisin Warner 15 is probably what we'll both eventually pick from the scrapyards after poking around behind all the 4L engines in Cherokees. It's a bit more durable and I think it's a great temporary package but it needs the skinny flywheel from a 4L engine and unless the plan is to move on to the ideal NV3550, it's probably not worth the efforts.
The NV4500 might work too but I wouldn't want to put that heavy superman thing in a stock Eagle. If I went to this the way my car is now, I'd give my stock AM differential about 3 hours before it randomly blows up due to sudden excessive wear. Honestly it's a wonder it has lasted this long.
If you just want to go to a manual and get the logistics figured out later like I do, avoid the Aisin Warner 5, four speeds like the Borg Warner T-18, anything Tremec (T-176...) and for God sakes if you ever find an SR4 in the junkyard, LEAVE IT! LEAVE IT! LEAVE IT! It belongs there. I notice you're a Nevada guy and I'm guessing somewhere near Carson City. If you feel like checking out Sacramento, you might have some miraculous luck when poking around the Rancho Cordova picking yards and factories. I want to call it a classic graveyard but everything there is either perma-scrapped or beautifully restored. Not sure if they know anything about Eagles but I know one has been sitting in their yard for months and they might be able to figure something out if you ask them about it.