Old body/New frame

[Pyrotechnic]

You gotta expect a harsher ride from a 3/4 or 1 ton truck when it's empty. You've added more spring and the truck is still the same weight. Now granted newer trucks may have slightly better springs, but the difference is a ~$5000 truck and a ~$30,000 truck. When you get either loaded down they will ride like Cadillac.

If you really want the best of both worlds, you wanna run 1/2 ton springs with helper air bags. That way you can have the ride soft unloaded, but when it's time to haul, just pump up the bags to lift the rear level.