DZ302 engine horsepower rating

[musclcar]

i know the DZ302 chevy engine shows 290 hp because i've seen numerous cars with this engine with the engine size decal on the air cleaner.but i remember somewhere reading that this engine was way underated in horsepower because of the feds.what is the actual horsepower these motors put out is it something like 400 hp or ?.i know you could ad on factory installed headers,cross-ram and the 493-512 mechanical cam from the dealer as options right. so does anyone know then actual factory flywheel horsepower i've got a bet going and hopefully i win thanks