In addition to the valve work, a quick and easy way to add a bit more is to port match the exhaust ports to the exhaust manifold/headers. most people don't realize that the fit between head and exhaust manifold isn't perfect, and often have ridges and offsets that impede flow.
1) use the gasket as a template for both (so they match each other) use a perm-marker or whatever will stand out and scribe the inside of the exhaust gasket for each port on both the head and the manifold (make sure you have the gasket lined up correctly with the bolt holes! )
2) use the markings as a guide and grind out a smooth transition in the head and the manifold. I usually start on the outside edge and widen it till it matches the gasket template outline, then work my way in smoothing the transition out.
Hope that explanation isn't too confusing! I don't have any pics of my previous projects, So I cant' show ya, but I wouldn't be surprised if there isn't a few guides out there in the interwebz for it. also, I haven't done this yet with non-square ports (like the dog-leg ports in the later v8's) so tread carefully if you have those.
Edit: should have checked first. quick vid on it for some other car. Concept remains the same. He doesn't go as deep a I would...I prefer to not only match, but provide a smooth transition for the air into the plenum. jsut be careful when taking allot of material off of headers...some of the cheaper brands have thin walls...it's easy to take too much off and cause weak spots that later end up as cracks. enjoy!