First off anything is possible..
I'd check the frames out and see what shape they are in. If they check out OK and aren't rotted in half or looking like it then drag them home.
From there check the engine.Look for any holes in the block or cracks. Pull the spark plugs and put some oil in the holes. I like to let them soak down at least overnight. Try turning it over by hand. Are you going to try and use this motor for a while? If so you will just about rebuild it replacing gaskets. Or go get that 401 and have at it.
The TH400 will handle it no problem as will the quadratrack if it has one still. It's going to need all new seals as well,so rebuilt it for good.
Same with every component on it and you'll have a nice Jeep in the end. Try and put it on the road as is after sitting for 21 years and good luck,keep a good set of walking boots and a cell phone handy.
You can almost bet every seal in that thing will be leaking or will leak very soon after sitting that long. Worth it in the end and it sounds like you get a practice Cherokee as well.
I'd be real careful with the wiring as well. It is old and likely messed up. Don't burn it down trying to fire it up. You can get just about anything you need for it still.
and by the way...........................