The 400 is much like the 383. Put some hi comp pistons in it,a big aggresive solid cam and some max wedge ports and you will be well over 600 h.p. But it will be a peaky unstreetable engine. The difference with the stroker is torque,and lots of it and hp in a lower rpm range,and usually a much flatter torque curve.It will make that same 600 + h.p but be streetable,lol..