1999 Chevy Silverado Vibration driving me nuts

I had a set of BFG all terrain tires, which were wearing out, and rightly so they had 70k miles on them. I noticed that the front right side was wearing worse than the others, and there was a horrible vibration at around 70mph. Sure enough when I purchased the same exact tires I was told they would not be warrantied unless I replaced the right side upper control arm, the pitman arm, tie rod, and had the torsion bars adjusted. This cost me an extra $800 (mostly b/c they marked up every part they bought by almost 50%). Anyway the truck rode fine for about two months, and now that vibration is back. It only happens at around 70-80mph. I just had the tires rotated and aligned, and it got worse (shakes the whole cab). Is this a tire problem or a suspension problem? Do I need to replace the same parts on the left side that were replaced on the right side? How do you tell if suspension parts have gone bad?

Thanks in advance for any help that I get.