If I were building an engine, I would first decide how it is going to live its life. Do I want a torquey, daily driver or a high reving horsepower motor. What is my budget? If you're below $3000, I would't run the motor above 6500 rpm. Then, I pick a cam that gives me the power curve I want. Then, I chose components that match the cam. If I chose a 6500 rpm cam, I would build a motor to match it. 180ccish heads, 9.5-10:1 comrpession, a 6500 rpm intake, and a larger carb. If I went with an off-idle to 5500 rpm cam or so, I would go with 170cc heads like the Vortecs, aim for a max compression ratio of 9.5:1, and a idle to 5500 rpm intake. When building an engine, I personally believe the cam should be the first part selected. Then, build the engine on paper and if it doesn't match your budget, start over with a different cam.