I might mention that there can be inconsistencies in gauges and sending units. I changed sending units one time and found the new one read 20 degrees differently from the old one. Many many people have changed to aftermarket gauges because it's widely known that the stock ones are woefully inadequate and inaccurate. I see you're still going by yours though. If you don't believe me or pretty much the entirety of information reachable through the internet that running at 212F is good and OK, there's nothing more I can do.
I will say to everybody here that despite what some people are ignorantly doing, DO NOT run phosphate type coolant intended for Asian cars in your older US built classics. Not only is it that coolant not particularly good at anything the chemical composition can be adverse to your gaskets. Improper use of coolant type is a real big issue with people who make their living keeping cars on the road and having to warranty what they do to keep them there. I could care less what random people do. I've seen people swear running straight water is fine. As long as you sell the car to some poor sucker before the radiator clogs up with rust flakes, I guess it might be.
As an example of incorrect coolant interaction, some time ago Ford unhappily discovered that their new latest and greatest company antifreeze meant to last longer than the old green stuff would eat the head gaskets right out of their 4.9 truck engines in about six months. Stuff like that happens all over because of people mixing and matching coolants. At that time Ford was unaware that there was an issue until they found out the hard way. I don't like to find out things like that the hard ans expensive way, but you can certainly do as you like.
If you must use a fancy antifreeze in your old car, try an organic acid tech coolant such as Peak's "Sierra". It's advertised as non-poisonous and such but the real deal is that it's composition can last up to 750,000 miles. The time limit is similar, making it ideal stuff for cars stored long term, like in museums. Toyota's coolant by contrast is good for only 50,000 miles. Yes, we all know of Camry's and such running around with umpteen thousand miles that have never had their coolant changed but that doesn't make it right.
As far as what other people recommend, unless their name is Edward Eaton, I'd be at least skeptical. Ed is the only ISO certified coolant tester in the world at this time. His word is gold, everybody else's, not so much. A majority opinion among people who make their living working with these things is pretty good advice though, and what I'm trying to relay here.
