Engine sputtering at about 65

Just be aware that at 18-20 initial timing and a stock distributor, your total timing when the mechanical advance is full in at 2500-3000 RPM will be around 40 degrees, and you will be flirting with detonation and piston damage if that happens. That is why I advised starting at 10 degrees advance or thereabouts... to keep you out of trouble. It may idle nicely with a lot of initial timing advance, but you have to look at all aspects of what is going on.

Yes, is can be a bit frustrating going back and forth between systems, but it will pay off in the long run to go through them all, sounds like this car has been neglected for a long time.

And, I agree with the statements on the fuel tanks... until you pull it a clean it out, you may continue to have fuel related issues and crud showing up in the carb. That type of tank clean is SOP for these cars.