Radiator shroud...

I noticed the stock water pump you are using with the lower outlet on the drivers side. Not sure but I think this is the same cast iron unit used on 273's/318's that doesn't flow as well as later aluminum pumps. I went with the Mopar 8-blade heavy-duty aluminum water pump, 22" 3-core aluminum rad, stock fan shroud and 180 degree thermostat. Absolutely no issues, even in stop and go cruising with 500hp Magnum with early LA front timing cover and belt driven accessories, 4-speed and 3:91's.