There is a difference between regular production anti-freeze like Prestone and the GM version. The GM is more expensive but is formulated to work better with aluminum radiators.
You should pressure test your system. You can buy a system/cap tester kit from a NAPA parts dealer for about $100. With it you can verify that your caps are holding the design pressure.
You can also verify that your system can be pressurized without a leak. The plumbing on the P car is very large with a lot of connections and turns. It is possible that the the junction hoses on the sub-floor pipes are worn out and permitting pressure drops in the system.
If you refer to a boiling/freezing chart (it is available on the Prestone anit-freeze web page) you will notice where the boiling points of the coolant are for varioujs pressurization of the system.
With no pressurization of the system, a coolant fluid temperature of 210 F is too close to boiling over.
Pressurized it is not a problem at all. In fact it is a good temperature to run at.
Doing this from memory (don't have the chart in front of me) I think that you are safe until something like 242 F with a 16 pound system?
If the car is cruising you will have enough air flow through the radiators to not even need the fans to run.
The biggest advantage of the aluminum radiators is the lighter weight. They are not more efficient then the brass/copper radiators.
The best radiator that I experience for the Pantera was Hall's Phoenix brass unit. With that one you could idle all day with the a/c on in Phoenix, AZ in the sun in the summer and not overheat.
I get the impression that some people think if the car isn't running at all times at 192 degrees there is something wrong. They are going to be just like the new, other cars and that means at times that they are going to push the limits of the system.
You can actually push this system a bit by using less flexible, or expandable hose like aeroquip and using higher pressure caps.
Basically what I am saying is that some of you need to get over all of this paranoia and accept the car for what it is...which ain't bad.
