you are creating more work for yourself.
The 97 4.0L is an excellent engine and will fit in your truck with a bit of work.
I forgot you will also need the 91-94 oil pan and pickup tube, and the engine mounts and plates for the 97 engine.
You can use a 4.0L from 91-2001 for your truck, but the ttb suspension means you need to make it fit using 91-94 OHV parts and the 97 computer is OBD II so you need the 93-94 computer and wiring.
Putting in the 89-90 style dash to me is making more work for yourself for a cosmetic gain, if you like that dash go for it, it is ALOT of work, there is a BII on this site right now that just got that done...
You need gears no matter what engine you run, removing the 2.9L and automatic in favor of a 4.0L and 5 speed is the best thing that ever happened to your BII, the 4.0L will make the BII scream and reliable, the 5 speed will save you headaches down the road from rebuilding the A4LD
These are big projects but if you prepare enough it will all bolt in.
Even with the later style dash you will still have wiring to do AND you are creating more issues to deal with, like the HVAC controls, air ducts, dashpot wiring, etc and you better get all the parts you need from one donor or you are opening more cans of worms.
I vote for gears and 4.0L conversion, the order and route you take to get there is up to you, based on the research you do now.
I looked at everything I could regarding the 4.0L conversion for almost 2 years before I dove in head first, it took me a full year of driving the truck to get it 100% correct, and then I ripped out the 5 speed and went auto for better around town driving, wheeling and most of all towing. it is a very common conversion these days.
Basically the only difference between a 91-94 explorer 4.0L and your EFI 2.9L (engine wise) is:
MAS
DIS ignition
the 89-90 BII has very similar wiring under the hood as the 91-92 Explorer, in the later years of the 2.9L they went to the later style headlights and under hood power distribution, in 90-91 they even made a MAS 2.9L making the 4.0L conversion even that much easier.
it is not difficult to convert your truck to integrate this under hood power distribution system, if you want the Gen I style dash with it, go for it, but its not required as you can see on my truck, I still have a 100% functional and 100% 1988 style dash, even with an OBD-II computer and 98 drivetrain.