read and pay attention to foot notes and requirements, different cams require or suggest different parts some of which are critical to the cam's performance. For example, if you get a cam who's power band doesn't come in until 2500RPM and you keep your stock converter or 2.79 gears your car is gonna be a dog. Different cams also require different valve springs so look at foot notes or contact the cam builder. Too heavy a spring and you flatten the cam lobe, too light a spring and you float a lifter at high RPM. You also have to know what you will be doing with the car, is it a daily driver, a highway commuter, a weekend cruiser, or a weekend racecar, choose one and stick with it. Don't build a weekend beast and then get pissed because you aren't getting 25MPG or it doesn't idle in traffic. My suggestion, look at what you have or plan to upgrade, piston's and compression, heads, valves and springs, rear gears, transmission, and select a cam that would best work with those spec's. I have an CompCam XE268H with AFR165 heads, a 2400 stall and 3:55 gears, and the package works extremely well together.