Why not just get a 2wd, jack it up a bit, fade the paint a bit more if it isn't already or paint it a single flat finish, put a loud exhaust on it, skinnies in the front, something big and fat for rear tires, and make it look like a Gasser. That whole grind or chemicals to strip the paint off bs is really,really stupid looking, especially on new cars. To me, if it has a real patina that doesn't affect the longevity of the sheetmetal, it's not bad, actually kinda earned, but even adding a bit of patina that isn't there let alone stripping the paint and letting it rust is well, just kinda fake. As for cracked White Walls......it's an XJ, not a 50's Jeepster and tires in that shape are just dangerous. When it comes to chopping it's top, I honestly think you need to print up and cut out then rearrange some pictures of an XJ or play with Photoshop. The XJ probably won't look as good as you think with a lowered lid. Power wise, a stroker with some sort of supercharged stroker poking through the hood and full exhaust with a cut out dumping before the crossmember would be interesting, wouldn't be the most powerful setup, but probably better than a junk yard smog SBC with a bunch of rusty crap and half assed exhaust thrown on it like many rat rods I've seen. I'd even consider gutting it on the inside and making aluminum panels to replace the stock stuff.
Jusy my thoughs.