I think there are clearance issues with the Offy and Clifford headers(I am not positive though). If you post your vehicle wieght, trans type, and gear ratio there a few guys here that might be able to steer you towards a good cam. Running the headers, the Clifford, and the 4 barrel with the stock cam and engine is never going to be "right" but try disconecting the carbs secondaries and see if it get's a little better in the top end.