a front universal will not give you death wobble.
does your steering box lower seal leak?
sometimes that is an indication of a cracked sector shaft, and a cracked sector shaft will cause death wobble before it breaks.
i am on my 4th steering box in my 88.
every time just before the sector shaft broke the seal started leaking and i got death wobble.

 

After changing the track bar I no longer have the death wobble issue. All I have now is a slight to moderate shaking in the steering wheel when making a slight turn. Its very noticeable and annoying but nothing violent or un safe. No need to slow down or stop.

 

Caster is fine then, I would look at tire balance

 

You think it could be tire balance even though it goes down the road smooth when driving straight?

 

YUP and it is cheaper than a axle u-joint

 

I'll bring it in and get the fronts balanced and I will change the u-joint as soon as I get some time. Too much snow to be working on the truck.