Cheapest ways to increase power

This is the reason I'm dropping in a 318 to my /6 '75 Duster. I know it's going to be pricey, but it'll be worth it.

I've got a stock /6, and I've been in two drags(stop light to stop light) both cars were ricers(sp?) and I smoked both of them. Fun times while using a /. But I want a V8 lol.