What size tires are you going to be running? If your going to be running 33's I'd suggest getting an HP D30 with the 297 u-joints and a 29 spline C 8.25 both from an Xj. Both would be plenty strong and an upgrade. Plus spare shafts would be readily avalible at a JY. You'd be able to keep your current wheels and they both would be the same width as your Yj axles.