6 Pax there are only 2 things that can make the gas overflow out of the carb. Too much pressure or the needle and seat being open. Also when putting the carb back together make sure the metering rods are in the main jets. The only reason I mention this is I bought a car from a friend that would load up stopped in traffic but would otherwise run fine. He had the carb an AFB rebuilt at a well know shop that had a good reputation but when I took it apart one of the metering rods was bent in a L and not in the jet. Anythings possible.

Wish I lived closer so I could stop by and help you find the problem.

Mike