I don't usually chime in. I read all these posts. I always feel I don't want to give the wrong info. But, here goes.
I too have/had this condition. I have 8inch wheels, tires about 26inch top to bottom. Bought new shocks, actually removed a leaf to lower slightly. New rear shocks.
Felt like every time I was on rough roads, or ruts, I thought I would be sent off into the shoulder. VERY SCARY!
Now in my instance, shocks were way to firm, but also, I checked my front toe after reading a lot here.
I used a tape measurer to measure tread to tread front, then behind front tires. I was tow out by about 3/4-1 inch!
I set mine as per specs listed on here, about 1/8 in. I did slight more because of the force when driving forward, so I did like 3/16-1/4 in. What a difference! I can drive truck much better. Its actually my daily ride with a 216. I can go on smooth highway and let go for about 1/4 mile with no drift.
NOW, there are some roads, highways near me that have roadwork, and I know what you mean about those ruts, and on that type of road, I white knuckle it still a little.
I just think after sooo much reading here, these trucks aren't/weren't made to go on these roads at these speeds.
I will be changing mine to mustang front end soon and coilovers in rear with 4link. I will have to because like I said, its my daily ride, and I will need to do 65 safely.
Top speed for me now is 53 comfortably, and that's with a t5.
So, I agree with those that said toe issue.
I also work for a major auto dealer in the serv dept. High end car. I cant tell you how many times I see customers who went to alignment shop and they are way off!
The equipment nowadays is awesome, but you need trained techs to set it up, and perform it. Local shops and chains aren't gonna cut it. Use the tape measure, it will tell you in 2 minutes.
Good luck and let us know.

PS??? One of the biggest problems with these sites is that when the initial problem is asked about, no one EVER responds with the fix. We all nee to improve on this, myself included.

Last edited by fiftee3; 08/26/2013 7:35 PM.

Phil