First, you need to get an infrared temp gun or at the very least a mechanical gauge. The factory gauges are not known to be very accurate. I would also pressure test the cooling system to see if there is any type of head gasket issue. Sometimes the cooling system will get cylinder pressure and cause overheating. Do you get little bubble in the radiator if it sits and runs until warmed up with the cap off?

I have a 408 stroker with a summit aluminum radiator and cheap single blade electric fan with no shroud and it never gets above 200 deg even in the heat of summer here in the high desert.