If it were mine and I was doing 35s:
-Keep the LP30. The strength diff between them IMO isn't worth the hassle. Properly setup, you'll break joints first anyway
-Lunchbox lock the front and selectable rear with 4.88 gears. Personally, I'd swap in an 8.8 over the 8.25. Plus the ARB is maintenance free in an 8.8 where the 8.25 can require frequent preload adjustments.
-Plate the frame at least to the transfer case area
-Long arm the front with an Ironman4x4 Fab kit. No doubt about it.
-Keep the rear simple and utilize good quality leafs with good shackles as well. Read: Ironman4x4 Fab
-Beef up the steering link(s) and add a steering box brace
Remember what makes an XJ perform so well. Lightweight and simple. Do your best to keep both of those a part of the build.