A shock kit is going to give you the best improvement in ride quality. The other options would help a little bit but since they don't dampen the movement of the suspension it wouldn't slow the movement of the suspension like you are wanting. Slowing the movement of the suspension is primarily what makes it feel "soft" and not just bouncy.
So if you have a 2-3/8 inch diameter axle the shock kit you'd want is the part # LC281255 or if you have 3 inch axles part # LC281281. view full answer...