I dropped the thermostat in hot water and it opened up, so it's good.

Thanks Stealthbird. I will try it without the thermostat in this weekend. The car seems to load up and not run very smooth, plus I'm getting black build up at the exhaust tips and subsequently on my garage floor if I run it long enough. I'm sure the carb is out of adjustment and needs to be leaned out. I haven’t got there yet.

Timing - I recently borrowed another harmonic balancer because my last one slipped. I guess it's possible that the one I borrowed is off too. But the car does not ping at all no matter how hard I get on it.

I have a mechanical distributor, so no vacuum to worry about. I haven’t tried an adjustable timing light yet.

As you mentioned, I do want to verify if the cooling system is operating well first. From there I can take a look at the timing again.

Unfortunately, I have to fix a brakes issue before I can take the car for another ride, but once I get that done, I'll be able to spend more time on this issue.