The 8-lug RPO was C6P; from there it's broken apart into two sets if you want to be super specific, 350 trucks typically got the 14-Bolt SF 8-lug, and 454/6.5L trucks got the 14-Bolt FF 8-lug.
On the ride of the truck, it's a 3/4 ton truck from the 90s, not a caddy; but you can still make them ride decently.
Start with all the bushings, 20+ years is way past the life span for the rubber bushings in anything, small things like GMT800 cab mounts can help but at the end of the day it's still a 3/4 ton Chevy.