Fasteddie is 100% right -- performance comes from tuning not just parts. You can eke out performance and mileage both from whatever parts you have. Nice parts, bad tuning, make for trouble.
Carbs are tricky, but learnable. Each carb type (Holley, Weber, etc) has it's own design and foibles. There's aftermarket books on each. Get one, spend a few hours under the hood and tune up what you've got.
Once you get the hang of it, you may achieve some Enlightenment and begin to understand your engine from First Principles -- eg. not just how much to turn a screw, but *why*. This knowledge will also help you problem solve too.
Whatever mechanicals you've got in there, assuming they're in decent operating shape, master carb and spark and you'll wring all the performance available from that particular pile of iron.
You'd be surprised what good tuning will accomplish. No amount of fancy product will fix bad tuning.
