I don't have the V8 but I did run 5100's for a few years. Mine were at 1.75 with tacoma springs for around 3" of lift up front. My advice is get the 6112 fronts if you can spend a little more. 5100's for me were awful on small bump compliance daily driving. On big stuff like speed bumps they blew right through the travel. I think this was all because of digressive valving but you'll find plenty of posts on the topic. On the other hand the 6112 gets glowing reviews.
My .02 since I'm now on rev 4 of lift kits and wish I would've skipped the early revisions. I currently have Fox but I think 6112 is a great shock.
FJ springs added zero lift for me but they do ride nice on stock shocks