I was wondering if I could buy a donor vehicle that runs good and just swap everything from it into my jeep. I'd swap engine axles transmission transfer case and all the computers and sensors. Would this work or is there more to it than that?
From one TJ to another, yeah, it's basically that simple. If, say, you wanted to swap a ZJ's V8 powertrain in, though, it'd be a bit more difficult. You'd need to create engine and transmission mounts for it, and possibly use different-length driveshafts.
But yeah, if you wanted to put the whole drivetrain of another TJ into yours, it'd be as simple as finding a donor with all the parts intact, and changing them over. Of course, the only real reason to do it that way is if the donor is cheap and has frame and body damage, or is otherwise unusable, but its mechanical bits are all in better condition than yours.
1997 Grand Cherokee Orvis Edition
1998 Grand Cherokee 5.9 Limited
They're straight bolt ins. I would use a 99 xj intake and tb with your sensors. Maybe a little better exhaust manifold too. Definitely use better injectors. The increase in displacement is rough on stock injectors.
Stock wires plugs and distributor are still just fine.
Just remember to break it in right before hammering it. Zinc additive for first 800-1000 miles then change the oil.
I guarantee you'll be way happier. You'll notice huge low end difference.