1994 Chevrolet Truck Pulling hard right

My truck has been pulling hard to the right. Only at high speeds. Recently on a trip I almost lost control of it on the Hwy. Had to drive slowly 200 miles home at night due to no shops open. Next day I went to a shop by me and they explained my Idler arm was bad. My pitman arm was not far behind it. I checked and saw they were right. They were both bad. So I replaced my idler arm and bracket, my pitman arm and at the same time I put all new tie rod ends on. 6 months ago I put ball joints on and packed the bearings. After fixing my truck, I took it in and had an alignment done. Got it back yesterday. Today I was on the hwy again and it is still doing it badly. I have to keep the truck at about 50 or less to be able to keep it from drifting. Mainly to the right but it does get like wavy. Any ideas on what this can be? I plan on trying to rotate my tires after work tomorrow but if it does not work can someone help me out?