1976 Chevy Corvette temp gauge

Engine Cooling problem
1976 Chevy Corvette V8 Two Wheel Drive Automatic 1oo, oo miles

is there any way to "balance" a temp. Sending unit (in head) to the gauge? I've rebuilt the car and replaced the lost gauges but the sending unit and gauge arn't matched! Useing an inf red therm. I get a reading of 175 at the gooseneck with a 185 thermostat but the gauge reads 200! I've driven the car many miles and know it isn't over heating but would just like to have the gauge show the proper temp. Will appericate any ideas you can give me! Thanks.