caster

I have an old, very beat-up pickup truck that has developed the "death
wobble" on the highway, like when it's going over 50 and hits a rough spot.
That will set off a violent shaking in the front end that won't stop untill
the truck slows way down. This is a 1994 Dodge Ram 2500 4x4 with the diesel
engine.
Death wobble is fairly common in these Dodges, which have a very underbuilt
front end. This truck spent its life getting salty in the winter; at this
point it's just about disintegrating. It's no surprise death wobble finally
hit.
Apparently, adjusting the caster can alleviate the problem (or so some say).
This brings me to my question: positive or negative caster?
Grocery shopping carts have a lot of trail (in effect, positive caster), but
are vulnerable to an effect similar to death wobble, where the caster goes
into a violent oscillation. One could naively conclude that positive caster
invites "death wobble." However, positive caster in motor vehicles enhances
high-speed stability. I presume that giving my truck a positive caster is
the right approach.
Yea or Nay?