Cheapest ways to increase power

To get a \6 to out run a GT Mustang is going to cost a bunch, very close to as much as swapping in a v8.

It could be done on a stock slant. A stock slant would stand a 125 HP shot of nitrous. With a header and a small four barrel carb even a stock slant would be a holy terror when the little blue button was mashed. Long as it doesn't lean out, you're ok. The more I learn about slants, the more I like um. They won't ever be a V8 cause they ain't V8s.