Mr Milliman is spot on. I have driven a number of these trucks varying from well worn to completely rebuilt suspensions, and they have varied from really scary to "I'll bet I can do 100".
As far as new shocks affect the ride, I have had the bottom rear shock bolt come off of the lower shock mount and could not perceive any difference in the ride.
Having experienced that, I do not believe that new shocks are the first item I would look at to solve a driveability issue. I wouldn't ignore the shocks, but I would not expect much of an improvement from replacing them unless they are rusted stuck.
Big trucks don't even have shocks, do they?
