What are the rear springs like? It's worth checking that the lean is not caused by a sagging rear spring. Measure the gap between the bottom of the chassis and the ground at each side. MMC had some problems with spring temper a few years ago, especially with +4s and early 4/4 Sports - this would be around 2007-2009 or thereabouts.
The new 4-leaf rear springs should be fine.
