I read through this thread. I guarantee its the tires. There is no way any other parts can cause wheel shaking while on the road while not on the brakes. Unfortunately you cannot diagnose this without a known set of non-shaking tires on a known set of un-bent rims. Tire shops can balance a set of improperly made tires 1000 times and it won't make a difference. They can also change out a set of tires 1000 times for other improperly manufactured tires and nothing will change and every "balancing machine" will also tell you that they are perfectly balanced when they are not.
I think you should find someone with another 4runner that does not shake on the highway, change out their tires for yours and drive around to confirm once and for all that you truly do not have a tire problem.
I had to do this to prove to the tire shop that literally every Goodyear tire in their shop was not round. All of the tires in their shop were manufactured egg shaped and after 4 (yes FOUR) completely new sets on four different sets of brand new rims being balanced over 40 times, I went and found someone with a set of General tires on factory 4runner rims and Holy Hell!! all the shaking was gone at all speeds!! It was as if I had just accomplished the impossible and it took the tire shop manager about 30 minutes of head shaking to finally realize that it was indeed the tires the entire time and there was nothing wrong with any part of the 4runner.
