Search on here, too much info on suspensions. You probably know all this already from the other Runners.
If you want the Smoothest ride you must go OEM (not OME) Toyota, I've not read of anyone coming up with a smoother ride than Toyota designed. All else is designed for heavier rear loads, added base weights from bumpers, winches, air pumps, ect. and of course for added suspension travel for the Serious off roaders.
Absalom pretty much sums it up here:
Absalom's Cookie Cutter 4runner Builds - New and Updated!
Luck, enjoy the latest Runner and look forward to the next. : ^ )))
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2001 Limited 4WD - 346+K - SunfireRed\Thunder Cloud; - 265/75/16 Michelin A/T2s - Fat Pat's 1.5" BL - StopTech ANGLED rotors - In series 699 trans cooler, New Yota1 transmission, All new OEM suspension front to rear.