AFB Tuning

I am not sure if the 500 cfm model has velocity valves [ weights ] in the secondaries. That looks like a factory carb.

What model is it?
Four digit # should be stamped on one of the mounting feet.

Does the carb have a large brass screw in between the idle mixture screws?

I can see one problem: it looks like it has a single plane intake.

Is the engine stock?