Slick 60's

When the front end was rebuilt, did you put in a drag link repair kit?

All bushings, kingpins and shocks where replaced as well as adding sway bar. But Like I said earlier, I have not had a chance to actually closely inspect everything, ( I know, i need to) just assumed it was still good since it has very little use.

"I could be wrong", but my gut still says it's not a tire. I've had a busted belt on a car once and it was rough as hell. PLUS the fact that I could not tell a difference after the rotation. I would think it would change quit a lot after moving the tire.

This seems to be so EVEN and speed dependent, not really ROUGH just bobbing. Certainly bad enough to make me a little nervous. I'm wondering about u-joints and drive shaft like Matt said. Could that cause it? Would explain how even it is and still basically be rotating mass. How do you check for that?

I missed the part where you said you rotated the tires and it didnt change, it would obviously change from one wheel location to the other if it was tire.

I am curious to find out what you do find now. The only other type of similar symptom I ever get is in my 78 Dentside when the track bar bushing wears out. Of course every suspension system can react differently to worn or bad components. I had another pickup that did the same thing and it was the track bars mounting bracket. Another idea is to make sure the new parts are the same as the ones that they replaced.