Check routing of fuel lines to see if they can be moved away from heat sources. Insulate fuel lines. Install non metallic carb spacer.
Mechanical pump? It may have a hole in the pumping diaphragm. Replace?
Installing an electric pump will often cure things, too.
Not quite sure your symptoms are quite right for vapor lock, though. But it sure did come to mind when you said 90 degrees, and I was pretty sure this is your first summer with the car.
Larry
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