Out of town for the next few days but will post more pics when I get back. Do not know the heat range on the plug at the moment. New to these vehicles. Truck has 164,000 miles. Impulse EBAY buy in VA and drove it back to New England. Drove fine. 16mpg hwy doing the speed limit. Idle at start up was strong. Once warm idled at 400rpm. Didn't sound the smoothest but never stalled out. Radiator had been replaced May 2017. Neglected to ask about this . Significant moisture out tailpipe. Did carbon test of coolant steam. Yellow in about 3 minutes. Pulled the head. Moisture in #1 and #6 cylinders.