I was going to ask if anyone had done this too. I had thought about the isolator and putting 2 smaller OPTIMA batteries in the slot where the 1 went and let them hang off a bit on each side. OR if you used an aftermarket CONE and tube intake, you might have room where the air box went. It might even fit IN the old airbox at that....
I'm wanting to hard-wire in some cigarette lighter ports in several spots in the XJ for power-on-the-go. I want a 3 way under the hood, by the retractable light (with a lighter in one, I smoke.)2 in the back of the hatch, 1 in the overhead compass (for my radar detecter) and maybe 2 in the back seat,in the rear of the console,by the ashtray. My sub-amp is under the back seat now, but it's already hardwired to the battery and that's where I also hook up my little 400 Watt INVERTER to now. Those built-in jumper/power boxes are nice too, but they don't fit under the seats in my XJ. I try hard to make sure that NOTHING bounces around when I'm empty. With as little room as you have in the truck to put things,even deciding which tools I cary under the seat, is a big deal. Even under the hood is kinda crowded.....