Rcimp,
Your assumptions are correct, no wire, no grounding concerns. Your gauge should have come as a gauge/tube combination..install the gauge in the instrument cluster, stuff the probe into the block and read the temperature.
I think the ONLY way this wouldn't work is if the assembly was faulty somehow. Could the little needle have been mashed against the glass on installation and it can't move? Maybe the tube integrity is kaput. The least I would do is test the assembly using a pan of hot water on the stove...if it doesn't work their, it's warranty time.
The nut and bulb assembly have a little seat that mechanically seal them in the original application. Could you have damaged the bulb when you mated it with the aftermarket bushing you installed in the '58 head.
Stuart
