Wish my Valiant ran this cool!

Do you eventually get heat from the heater? If so, the thermostat is opening, because there is no coolant circulation with it closed. Since you've checked the guage, the next steps would be to check the sending unit and the wiring/connectors. I'm away from my books, but didn't most of the smog motors run 190-195 degree thermostats?

If you've gotten used to the new alloy block cars that put ought heat in the first mile, remember that these oldies use cast iron. By comparison, they take forever to heat and to cool down, too