As far as the meanest beast out there, I would either go with a supercharged 406 with AFR 210 heads, or a 598 with AFR 355cc heads. Either of these motors with a hyd roller cam that makes power from 2500-6500 will make between 800 and 900 hp on pump gas. You will be looking at between $12000-$15000 for either of those motors, but it costs alot for that much hp while being streetable. If you wanted to go all out, you could build a blown 598 with AFR 357cc heads. That will produce around 1300 hp on pump gas, but you can look at about $20,000. Other than that, just go with a 406 with AFR 195cc heads and a hyd roller cam. That will put you at around 550 hp.