Time to Fix It Right

Added a bit more info above. The heads are definitely stock. dano, those are all good suggestions and things I'd like to do eventually, and you're right that it's difficult without more knowledge of the internals of the engine.

I'm not opposed to pulling heads at some point (have helped a friend with a head swap before). But given how little I knew the last time I tried to tune up the engine, I think Murray's suggestion of a tune-up is probably a good place to start.

I'll do some forum searching but maybe someone reading already knows this -- is there a good, comprehensive guide to tuning up a carbureted V8 starting from the basics?