Autometer Full Sweep Electric Transmission Temperature Gauge for the Chevy Camaro.  Autometer is a leader in after market performance gauges.   

This is from the Cobalt Series of gauges.  Its diameter is 2 1/16" (52.4mm) with a full sweep and electric.  The range is 100-260 degrees F.   

The gauge comes with 1/8" NPT Sender, and a 3/8" NPT and a 1/2" NPT adapters/fittings.

If mounting in a steel pan, part 2260 bung in the accessories section is recommended.