You already have a good suspension just improve what you have. Look at the Ride Tech system. I have put many in all different cars and trucks. Check the shock wave double adjustable system with a heavier sway bar and then use the tri angled 4 bar for the rear.This truck will handle like a sports car then and you can set your ride height at 3 different positions( use the leveling switches for the best control)

 

Agree with above, those suspensions are remarkably similar to GM A-body in design and unless you need something narrower for some-type tire clearance you'd be hard-pressed to improve on it for performance use as far as general architecture goes. Just drop spindles to keep the geometry close to right, if you're lowering it, and the sway bar/shocks etc.

Modified front clips are so common on older trucks because stock suspension was usually so awful on them. GM fixed it good in '88 and that was that...I had a lowered dually that year with the usual simple mods which handled exceptionally well, after suffering with an '84 for years. Certainly no need to change much.

If you really did need a bunch of extra tire clearance I'd be looking into...well...GM A-body, probably '73-'77 which are pretty heavy and would be up to the job. But there would be a lot of fabrication to do between the suspension and firewall.