Roadking53, if it helps ease the concern of being mis-matched, my original 1957 gauge registers very close to what yours does. I have also installed a secondary mechanical dial gauge because I was concerned of the running temperature. With the AutoMeter gauge reading 180 degrees, the factory gauge is between the first and second marks.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy