I have run 890, 891, LC 9.25 wraps and now 861s. The 891s are nice coils. They carry towing weight well. Since you are going with the COs, you can dial in exactly the height/rake you want.
When I went from the 890 to the 891s (about the same height but stronger spring), I added a PHB drop. I immediately noticed the difference. Without the drop, I would feel the rear swim (left and right) on bumps. The drop eliminated that feeling. Yes at 3", I would suggest doing a PHB drop.
The stock position of the PHB is fairly level. Upon compression and rebound (normal road driving) the axle moves in a mainly vertical motion.
This allows the arc of the bar to be in a mainly vertical direction. When lifting, the axle is pulled toward the passenger side. This also causes the PHB arc to be more diagonal. This diagonal arc causes the axle to move left and right when compressing/extending (more than a vertical arc).
A drop and adjustable bar allow the axle to center back up. The adjustable bar is a bolt on but retains that diagonal arc. This can be felt as "bump steer" of a swimming feeling. When properly adjusted, you can minimize the gas tank contact. Steve and I talked about this contact and I made adjustments to the tank skid that i sell. Steve actually runs one of my skids.His bar looks like a great option and there are many out there.
The drop brings the PHB back to a more horizontal position (like factory). Because of this, The arc is more vertical again (under normal street driving). Also since you have not lengthened the PHB, the clearance (driveshaft and gas tank) has not changed. The drop must be mounted in a vertical position which sometimes takes a little grinding. It must also be welded on.
Diff drops. Long debated. See my post #3
http://www.toyota-4runner.org/3rd-gen-t4rs/124476-diff-drop-specs-measurements.html I have over 100,000 miles with my diff drop and have had no issues.
The CV boots will probably rub after lifting. This rubbing can wear thru the boots. Stretching your boots can help. See my post #41
http://www.toyota-4runner.org/3rd-gen-t4rs/87397-diff-drop-3.html