If your tailpipes are that black you are running too rich. Makes me think that the primary jets are too big and/or the metering rods are too small. The lighter springs will cause the vacumn advance to come in sooner and with the weight of your car that's not necessarily a good thing. What size is the carb and what size are the primary jets? Much over 600cfm and you're over carbed. Are you coming to the Nats on Friday or Saturday?