Just put an 83 engine in my 80 with a set of 83 gauges the engine has appox 100k runs strong no leaks, no water in oil, no oil in water, does not leak out of weep hole. Does still have an original water pump installed. When driving 1st through 4th the temp indicates just above mid gauge shift to 5th Overdrive 70 -80 mph temp gauge climes to just below the over temp mark. Out side air temp for my driving has been 85 or cooler. Do I have an over temp issue I would except the gauge to run cooler shifting to 5th slows the engine and more air through radiator. Is there a difference in temp sending units for the gauge change put a 150 mph speedo and OD tach with cluster. Do I have a gauge problem mismatch with sender how do I check or do I have an overheating issue.