While I'm sure you could mod them with cams etc. in my research if you want the biggest bang for the buck you supercharge. I like procharger for a few reasons, others say Whipple is the way to go because of installation.

Regardless, you dump your few grand a motor and are done Vs. a bunch of odds and ends mods that don't net what you'll really want. When you do the exhaust get cheap aftermarket aluminum, nothing makes all that much difference.