'55 Chevy pu. Steering problems

I have a '55 chevy pu I'm working on and I'm trying to improve the steering. I had power steering installed without the independant suspension. I have a problem with the truck wanting to follow the rutts in the road and when at high speed the truck wants to jump to the right. I've checked all suspension components and everything seems to be tight. I have new tie rod ends, the king pin is tight, and there seems to be no unusual movement in the springs. I had it aligned and the mechanic said that the caster was off a little bit and I needed a new axle. I don't think he adjusted the tappered shims and that is what I think is probably the problem. There is an upgrade to the wheel bearings that says it improves the rutt following but is this my problem?

Thanks