Dean,
Did the car previously run cool without overheating? Is this new behavior? And, is this a newly rebuilt engine? If recently rebuilt, and that's when you started experiencing the overheating issue, I would check that the head gaskets were not installed backwards. Depending on the gaskets used, you may be able to tell by the location of the tabs that stick out from the head, if any. You'll need to check with the gasket manufacturer.
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