FYI: 97 (not 99) was the year of the body/interior makeover.
You cannot EASILY get 6.5s in the front doors of a pre-97 XJ. You can, however, mount them ON the front doors.
You would have to put an MDF ring OVER the door panel and remove the stock grills (an easy process, BTW). If not, 5.25" are all that will fit, because the door panels are basically a flat sheet of cardboard wrapped in cloth and/or vinyl. There is ZERO space behind them. I used to have to use plastic washers on the panel clips to pad the panel out far enough that the speaker did not hit the back of the panel when I was playing music.
If you have the time/energy, I would get MDF rings, wrap them in vinyl, and attach them outside of the door panel, being sure to screw them TIGHTLY into the inner door skin. I would then mount 6.5s to these rings and use a good pair of grilles.
If you have manual windows (like my first two Cherokees did), then you are screwed because the cranks will hit the spacers.
What color is your interior? When I did mine, I bought extra door panels at a junk yard so that I could modify the ones that I had. Jeeps are pleantiful, and the panels are cheap and easy to find.
Also, do you have the rear hatch speakers or the ceiling soundbar? That makes a big difference.
lastly, DO NOT try to use the aftermarket plastic mounting kits for a HU. I had to re-use the metal one that holds the stock radio, but it is worth it, because it makes the best mount for a deck. I broke 2 different aftermarket kits. You have to re-drill the metal bracket (it is easy) to move the unit down and forward to get the HU face to line up perfectly, but after 3-4 tries, I got it perfect and my HU was allowed to do its job preventing skips...plus the bracket never broke.
It is VERY difficult to get the wiring run to the dash location in an XJ. I used a LOT of blood to lubricate the cable runs (LOL) but I found the driver's side to be the easier path for RCAs. The HU wire harness does not have a lot of room to be crammed, either. Be careful that you don't cut any wires on the duct that runs behind the HU. I taped off the sharp edge with electrical tape and slid a sheet of thin cardboard over the top of the HVAC controls to keep the wires from snagging.
Let me know if you have more questions. I have done literally 20+ different installs in Cherokees.
