Because the HP number doesn't tell the whole story. A 400 HP 360 will be much easier to drive on the street, require less stall and gear, last longer and probably get you better gas mileage to boot. Note that they didn't start taking pulls on the dyno until 3600 rpm. Drive around at 3600 rpm and above and see how comfortable it is. Engine Masters is a great mag but you have to read between the lines when it comes to dyno tests.