ATK 5.9 Magnum crate motor horse power

Wanting to be around the 375 HP range don't think my car would take any more - stroker ok but want the magnum set up with roller cam and straight down bolt intake (not LA style) looks like the ATK 320 HP is a stock motor just letting it breath better with carb and exhaust
Why in the world would you want the straight down bolt intakes, there is hardly any selection in intakes, and even used ones are not cheap.