Gauges going all the way on startup + smoke

Looks like you have a '67 dash in your '69, so, I would imagine work has been done in that dash before. A new solid state IVR is in order here to start. The gauges may have survived. Only after you install a new IVR will you know if they work and are still accurate.

hopefully they were not damaged because it was just a few seconds, but as you mention, only with a good regulator voltage I will be able to tell.