You're 'gonna need an emergency RENIX kit. LOL. Well lucky for you if you do get the '88XJ is the fact that there are true experts here at
! Without their expertise I'd be looking for a different machine. With that said, place your finger into the tail pipe, and see if there is much soot left on your finger tip.
How many miles?
If you ever get a leak from your injectors, (off of the side of the fuel rail.., over the exhaust manifold), you are libable to burn the XJ down. The experts here have shared, will share the correction needed.
When you say the 88 will only be a wheeler, does that mean you will only trailer it out to the turf? Death Wobble is not a joke, lol.
One thing about the RENIX system is that the ground cables/straps need to be bigger, new, clean, and making good connections. Extra grounding does not hurt either. See if that has been done, or not!
The low mounted alternator requires spares if you do muddy creek crossings, etc., as you are most likely going to short it out from the contaminates. Therefore you will probably want to fab up the alternator into a higher position, sans the A/C.
What kind of lift height are you intending? What size tires? One thing to remember is that the front wheel bearings are narrower than later years, so they don't like wheel spacers. I would imagine that 50 pound, or heavier tires could also prematurely wear them out. The fix, besides replacements, would be to obtain a different axle, which is something the mod. guys will guide you properly.
If you are 'wheeling', are you going to get a winch? If so, you might want to consider an extra battery, etc., which means you will want to relocate your air filter box entirely, and replace with an alternate setup, i.e., a snorkel, or a redirection of a filter into the passenger side cowling, through the firewall. Later model XJ's make that task a bit easier due to the location of various parts. I'm not going to go into that discussion any further at this point.
That's all I can think of at the moment.