Thanks everyone! The weekend is coming up and I can do more diagnostic based
on your suggestions.

I had not checked the heat risers or the base of the carb for hot/cold.

The engine is tuned to spec. The temperature was 27 degrees with the humidity
around 15% when I first noticed this although its doing the same thing at
higher temps and humidity. The engine at each instance was cutting out at the
first light after coming off I-64 at 65mph. indicated.

David