Well, not exactly. With a flathead there are fairly definite limits unless you go to real extremes. A nearly stock SBC or 5.0 Ford will out perform a street modified flathead. Flathead have major breathing problems and there is really no getting around it. In fact, most older OHV 6s will out perform a flathead if modified properly. To me a flathead is for nostalgia, not for performance (but love seeing what I can get out of them). If I wanted performance in a truck I would go with the six cylinder. Your horsepower comment would apply much more to the six than a flathead.