Not sure about a lot of that, but if you're running a PO's non-standard driveshafts (which might not be obvious at a glance), I'm guessing a change in height could really screw you up. Also check the LSPV height, and make sure extended brake lines don't get in the way of anything after lowering.
If you plan to run sliders, check the mounting points. Some attach where drop-brackets need to go, so you can't run both. Radius arms don't have this issue.