Just bought this older restored car. Car runs great (272), does not overheat but when I shut it off and let it sit for about 10 minutes, it will not start until engine cools down to about 140 degrees or lower. I insulated the fuel line, ventilated the fuel tank, and put in new fuel filter. Need help, suggestions. At a loss...

 

Try getting a heat shield for the starter. GM had problems with heatsoak of the starters for years, and finally decided to put a heatshield over them to keep some of the heat from the exhaust manifolds. I even had made me one out of a piece of scrap aluminum, drilled to fit the bolt pattern of the starter head and went part-way around the starter.