360 Street/Strip Cam?

Use magnum manifolds pointing forward. Cobble together a cheap ebay turbo kit. You could get the power number required for a couple grand without messing with anything else. I was half joking before but I'm also somewhat serious. Except for nitrous it's probably the cheapest route. Your biggest enemy in the stock bottom end will be insufficient ring gap but if you gap the rings and have a decent tune then the 600 hp or so is entirely achievable with a stock bottom end and a mild cam.