Barry,
I'm still catching up, was gone for a few days. I saw the post on the carb prices, yikes X2! I think I paid $85 on the 'bay for a NIB, still had the Kaw/JD labels on it. Like I said, it's been good since I changed it. I did find all that stuff wrong with the old one, so I know that was the problem.
I'd guess, if you had the time to keep watch, you'd be able to find a good one for less than JD new price. I believe that's all you haven't tried or done to fix it. I hate to "shotgun" a post with possible fixes, but that may be a good move to replace the carb with the late style unit.
I'm thinking out loud.........you're sure it's flooding over from the heat, gas boiling out the top and into the manifold, we know the fuel isn't getting into the carb from the fuel supply line (it's shut off), I'd bet on the carb being the problem.
Fred