I think you should look more at the HP goals of your engine. There are several rules or formulas but one is, HP = 0.25714 CFM x No. of Cylinders. In other words it takes so much CFM of flow to support so much Horsepower, so what is your goal? Next what is the RPM range you want to run, or that you have parts to support? Runner length and size is determined by how many RPM you want to run. Pick your HP and RPM, then pick best bang for the buck in cylinder heads that have the correct flow and port size. Good engine software, makes these decisions easy to make. After you pick the heads, then the camshaft, intake, and headers to match the heads gives the best results.
I don't build lots of engines, but I get so many guys who collect a pile of parts, and then expect me to make them 800HP. Then I look at them and say I can not make 800HP with these parts, because you selected parts that don't complement each other. So do you build the engine, and they are disappointed with power output, or do you tell them to take it home, and they are disappointed because you won't build it? Most of the time it is not an issue with bolting it together and reliability, it is quality results.