Thanks, I see that now -- it looks like the mount popped off the small stud on the back of the voltage regulator. I'll try to reattach it or buy a new one. I assume this not being connected to the regulator would prevent the gauges from working properly?
Redneck, yes, that is a quartz clock movement typically used for wall clocks, but with a housing that fits and is identical from the front -- see photo. I started by designing one for myself and then eventually selling to others at a price typically 50% below other repros (if a repro even exists -- many models are not made by anyone else). Over the past three years, I have sold close to 1,000 quartz clocks for fifty different models, covering 1960-80s Mustang, Cougar, Camaro, Corvette, Chevelle, Firebird, GTO, Mopar and Chevy trucks. If you are looking for a particular model, direct message me and I can send you to my website (you can also find them on eBay or at NPD.)