That engine was built 13 years ago for a dyno competition, the guy that owns it was on another thread saying he drove and raced it for like 10 years.
It's not meant to be a build that you copy but the main idea how is there. In the article he states how he would do a simplified version that anyone could build. The availably of parts for building high hp sbm now is a lot better compared to then. Your saying a set of trick flows or similar heads with a big solid cam and around 10 or 11 + to 1 cr can't make 500 hp ? Don't think anyone saying 318 is the best way to go for 500 hp, to me anything over 425-450 hp I'd start seriously thinking Big Block maybe a stroker sbm but to me they don't make any sense. Under 425-450 hp any 318/340/360 would do.