416 stroker temp?

You would think if the gauge or sending unit went bad you'd get really inaccurate readings. Too lean in the carb could cause it, and yes timing as well. Have you looked at the plugs? It the idle erratic or fine?

Two small electric fans have a reputation of being inadequate. Many have solved their overheating issue by removing them and using a mechanical fan. But in your case I would look into that last.