Unfortunately there really is no bang for the buck if you want to keep it stock looking (other than gear). Headers are the number 1 bang for buck on a 440, followed by a cam, then intake manifold.
Stealth heads, or port your heads, 800 AVS, maybe a little more cam, but you don't want to go crazy with exhaust manifolds. Lots of people like the 528 Purpleshaft for exhaust manifolds as AndyF had good luck with it. I can't speak from my own experience though. Or you need to stroke it.
More gear always helps too
It should still smoke those redlines IMO. Are you sure your timing mark is accurate? Have you verified it? Do you know what the comrpession ratio is? Exhaust manifold heat flap stuck?
