funny this thread popped up. My family has owned many 4runners
1 - 2nd gen
4 - 4th gen
1 - 5th gen
All posts consistent with what I have experienced
Recently bought a new 5th gen. Had to test drive 5 vehicles to find one without the steering wheel vibration. Found one and got it.
One of the 4th gens had it since the day it was purchased (new). between 60-65 mph. Tried everything to get rid of it (balancing, rotating, tire change, cv axle, tie rods, bearings, etc) with no luck. Eventually just learned to live with it.

hwell:
Problem in 5th gens too. Test drive, test drive, test drive... I only knew to look for it because of my experience with 4th gen.
All the 5th gens I test drove (brand new) had it to varying degrees (b/w 60-65mph). I found one that only had very very minor shake/vibration if you looked for it at 63mph.
I have concluded it is something drive train design related (unbalanced), really not sure
Have not had any functional issues (although bearing did go out at 130k in the 4th gen with vibration), just annoying

uke: