Hello rm69Dart. I have just been through the ringer on getting my 440 68 Dart to run cooler in our scorching Arizona weather. Have you checked the flow pressure of your cooling system? Coolant flow is a major component often overlooked. This can be checked using a simple store bought line pressure gauge found at Home Depot, Lowe's, etc.. This is typically used to check pressure at a spicket. Coolant flow pressure should measure in around 18-20 psi 2000-3000 RPM. I contacted and spoke to Ron Davis last summer and this was his advice to me. I found out I was only running 8-10 psi 2000-3000 RPM. I ended up installing a new Flowkooler water pump and aluminum Mopar water pump housing and I now flow 20 psi at 2200 RPM. You can check this with the motor cool. It does not have to be at operating temperature according to Ron Davis. Ron informed me that most aftermarket water pumps simply do not flow enough volume. This update lowered my cooling temperature significantly and was a major component for successful temperature mitigation.