Have you thought about putting a Banks system on? Did mine, and it's all stainless, so no more rusting out! I bought the complete system headers and tune, but if I did it again, I wouldn't bother with the tune. BB Chevys like free flowing exhaust, and I'm sure that's the biggest part for improvements that can be made. Need a set of good used exhaust manifolds?
Happy Glamping, Norman & Elna. 2008 Winnebago Adventurer 38J, W24, dozens of small thirsty ponies. Retired after 40 years wrenching on trucks! 2010 Ford Ranger toad with bicycles or KLR 650 in the back. Easy to spot an RVer, they always walk around with a screwdriver or wrench in one hand!