It's running lean at cruise. What's your vacuum reading at that RPM? You could jet up on your primaries and/or play with the power valve. Are your carbs mounted sideways? Do you run a 1:1 linkage on your primary/secondaries? What are you running for fuel?
You said, "factory pulleys." What drive are you running , 1/2" or 8mm? And what is the tooth count on each of the pulleys.
Does it idle ok? If you're driving it on the street why do you have the timing locked out? I know others are going to disagree, but I'm a fan of using one blue and one silver spring and not locking it out.