99XJ Engine trans swap

I have two 99 Xj's a two door 2.5/AX5 (engine shot) and a four door with 4.0/AW4 with 80,000 miles(wrecked) What is involved in installing the 4.0/AW4 in the two door?
Concerns:
1. Can the 4.0 ecm be plugged into the 2.5 wiring harness, or does the whole harness have to transfer with the 4.0?
2. Obviously the AW4 will need its' controller and attendant wiring/sensors, is this a huge undertaking?
3. Since both vehicles are 4x4 and complete what needs to be changed besides engine, trans, tcase, drive shafts? engine mounts, crossmember, radiator and exhaust?

This will be a DD and no offroading, looking for something that gets better mileage than a 454 4x4 Dually.

Would I be better off to find a good 2.5 and install it? I know of a 93-96 XJ with 2.5 with ony 90,000 miles, can this engine be used with appropriate sensors, accessories from the 99? TIA, Shack

The 4.0 engine to ECU harness certainly needs to be swapped and I believe the engine compartment one does as well.

Not sure about the TCU, since it's a manual you may not even have a connector for it. Might need to drop the dash and swap the harness behind it too...

Other stuff - driveshafts, engine/trans obviously, radiator fan assemblies, possibly the radiator itself (don't think so though), the engine mount brackets that bolt to the frame rails. All need to be swapped, but it's just a bunch of bolt-on crap, and finding donors for a late model 4.0/AW4 rig to complete the parts collection should be easy if any of that is damaged or missing on your donor.

Believe you should be able to simply bolt your sensors, intake, accessories etc from your 99 onto the 93-96 2.5 if you want to go that route. Might as well change the pilot bearing and throwout bearing while you're in there if you do that.

Swapping the AW4 can be annoying, you'll have to route your shifter cable through the firewall in the right spot, involves pulling the carpet up and swapping the blockoff plate and shifter handle on the trans tunnel as well but that's easy. If you do this you'll have the dash and console out for wiring changes anyways, so moving the carpet is no big deal.

I don't know if the crossmember is the same. I suspect it isn't, use the one from the donor if it looks different. Exhaust is also different as you noted, at least as far back as the cat.

Oh, the tcase shifter linkages are different to some degree as well. Use the ones from the donor.

First, kastein, thank you. Since the engine trans swap is more than I want to tackle, I'm OK with the mechanics of it, not the electrical, the swap is out.
I've been offered a 95 2.5 with 60K on it. Since I live in Alaska,(-No emissions laws here) I wonder if I can strip all external parts off and substitute the 99's externals. Is this doable? Is there any thing to prevent me from doing this? Since both are MPEFI engines they should have the same essentials as far as sensors etc. Any thoughts?

Should work IIRC - I don't know the 2.5 all that well though, very rare around here in XJs. I would say less than 1% of vehicles.

Just swap manifolds, all accessories, and all sensors onto the 95 motor from your 99 motor and it should never know the difference. It looks like there are two heads for those motors, #117 and #403, corresponding to TBI and MPFI years, and both your recipient and donor are MPFI and everyone says they are compatible anyways so I would just go for it.