Workhorse W or P chassis.
Easy to tell:
P chassis front suspension is independent-- looks like a Chevy truck.
W chassis has solid front axle.
So suspension upgrades are VERY different.
Also, have you had the wheel positions (best) or axles weighed?
Have you set your tire pressures based on your tire manufacturer's recommendations for that actual weight-- if individual wheel weights, use the heavier wheel position to go to your tire manufacturers PSI table. If, for example you are 20 PSI overinflated, you ride will be terrible.