First, are you sure the height is off left to right and it's not the bumper that is bent? The lower part of the passenger side of the bumper looks a little pushed up.
How much does the left vary from the right? A stock coil isolator gives about 3/4". So maybe just add one to the low side. It may still be off by a little bit, but so what. That would be what I would probably do.
....Or, you can (I think, double check though) cut a little bit off the bottom of the coil spring to level them out. Double check if you can cut off part of the lower end of the coil without ruining them. Because the coils are NOT a flat bottom, I think you can. If you can for sure, cut a little bit at a time of course (you can always cut more off). If it were me, I would just start by cutting off maybe 1/2" (from the end of the lower part of the spring of course) and see how much that lowers it and then figure from there. Know what I mean? DO NOT CUT 1/2" up vertically, but ALONG the spring. I would always underestimate how much to cut off, again you can always cut more off. However, the front might sit a bit lower than the back, although that depends how you are currently balanced from front to back. So, maybe just add a stock coil isolator to the low side and it may still be off by 1/4", but that should be virtually unnoticeable without a tape measure.
If you are careful and have an angle grinder, you could just jack up the frame, disconnect shock, coil retainer clip, sway bar, and let the axle droop, and then rotate the coil to get a good angle to cut off 1/2" or so at a time. That way you don't have to pull the spring out, put back back in and test, then back out to cut etc.
Also, is the lift in the back even?
