If you do some more research, you will find that installing higher flow rate heads and not changing anything else usually results in marginal gains in torque and HP and, sometimes, has the opposite effect. Intake, fuel volume, cam, heads and exhaust work best in a given RPM band when they are a balanced system. Flow rates and flow velocities being in the optimum range are critical. As one increases flow volume capacity in a given system, the power band RPM range increases in order to maintain flow velocity. The auto maunufacturers do a pretty good job of matching components. So it's common to find that in order to get the potential gains from a new cylinder head, one also has to change the camshaft and the valve springs and the intake and the carb [injectors]....... and so on. The point here is if you really want to build up an engine with a given power curve in mind, then start with a bare block and select the components that will get you there.
Case in point involves Mustang owners. The Mustang Ford 302 had the E7T heads. The later Ford Explorer 302's had GT40P heads which have higher flow capacity than the E7T's. So to gain some power the Mustang guys figured they could put on the GT40P heads and get a few more HP which they did. They also had to put on new exhaust headers. Because of a change in spark plug angle, the E7T headers won't work on GT40P heads. But, they soon realized that the factory camshaft was limiting the full potential of the GT40P's. So, get a "Bigger" cam. Whoops....gotta get new valve springs too. Gosh, stock Mustang intake is limiting flow. Get one off an Explorer. That's funny, it matched the GT40P heads. So, what started as a head swap ended up being an entire top end build. There are many articles written that tell one just how to do all of this.
I went through all of this planning and research when deciding what to do with my engine build up. But, I did realize that a stock Ford 302 with a slightly bigger cam would sound good and have enough torque to spin the tires really good. So, decided to save some money and just update the camshaft. We'll see how that works out and, someday, if I want to jazz things up a bit, I can always tear into that engine and add more power.