The stock intake and exhaust manifolds are incredibly crappy.
Headers, for sure, and Offenhauser makes aluminum intakes for 2 or 3 1-bbl. carbs, as well as a 4-bbl. Cams are available, and higher-powered ignitions. Raising the compression ratio and various head porting techniques can be very beneficial, but only in conjunction with the other upgrades. 400hp is do-able!
Like anything else, how much you wanna spend?
