Heavy steering is usually the result of too much caster correction.Something else I want to mention--the steering feels too heavy to me - definitely heavier than my '93 LC I had before this '97.
Personally, I prefer the heavy feel since I put on the DVS arms. I was able to zero out toe which lightened the steering a bit while still maintaining good road manners and strong return to center.
I would suggest getting the truck on a rack and check the caster and toe.
Also, the "notch" in the straight ahead position indicates worn knuckle bearings.