Well I have two venues to partake now.
This info was provided to me by a fellow TD'er who knows his stuff:
In your pic, the sensor on the cylinder head just to the
left (as you look at the pic) of the distributor cover. It
has only one wire going to it. The parts manual calls it
both of these and references two different part numbers
also:
Sending unit, engine temp gauge 4504203
Sensor, engine temp 4437313
I don't know why it has two listings and two numbers for the
same item (and I am looking at the 90 factory parts manual).
The 2 wire sensor in the t-stat housing is the coolant temp
sensor and is what the SBEC looks at to see engine temp.
The two sensors are not interconnected in any way.
So, I went ahead and ordered that new sensor today and it will arrive tomorrow.
The other option I have is heading over to Heath Farquhar's house if this does not work, and we are going to run a voltmeter test on the gauge itself.
I'll keep you posted.