Are you positive it is not over full? I think it hold 6 quarts with an empty filter.
I don't see the valve guides being a problem. They are not known for leaking oil, and the oil to the rockers is metered, very little oil goes up there.
Have you tried removing the air cleaner hose? Possibly the air cleaner has too much oil and is over flowing into the carb.
Is the crankcase breather tube open?