bigmanjbmopar
Newb with a view
I have had bad sensors out of the box, if the wire to ground pegs the gauge then that works it must be sensor, don't over complicate it.
If you don't have a coolant recovery reservoir, after the car cools down pull the cap and check the level. Add water until it's about 1/2" below the fill neck. Do this 3 or 4 times until all the air is purged. If you do have a coolant recovery, just check the cool level on the reservoir and top off when needed. If you don't already have a set I'd really recommend a good set of mechanical aftermarket gauges to monitor your motor. In the 60s it was one of the first additions to any rodder's car.