Well all of the described engines WILL produce 400bhp, but the differens is HOW they will produce it, and that is what most people seem to forget.
The wery first thing people should do is to think how and where the power should be, should it be torque or high power.
BUT the cheepest way to get 400bhp is std engine 2wd manifold, rs500 cooler t34 .63 or t38 and live map on minimum light blue / greys