BJ they do have a website and I think it is
www.evanscooling.com. I will find the boating journal where they have an ad and post it on this website. I did speak with them to find out whether I could use this stuff in my Caterpillar marine diesels and they said yes. As you can imagine, draining eight gallons out of an engine you can't get underneath of- without spilling any into the bilge or the water- is tricky. But they have a lot of experience with it in fleet use and I am going to try it out.
Now, having said all that, I agree with Ron that the problem you are having is not a coolant issue, although changing to a coolant with a higher boiling point might help. And, I don't think ERAs are more prone to overheating than any other mid-engine car with a long run between the motor and the radiator. So, the problem must be that some part of the system isn't working as it ought to, and my hunch is that the system is airlocked somehow. We have had a number of postings on how hard it is to get all the air out of the system.
Good luck with all this. I will get Evans' access info up on this thread as soon as I can, but I still think it is a function, not design, issue. Incidentally, you might try Grand Touring Auto in Laurel. They maintain an old GT40, 1072, and have moderate familiarity with them, plus tons of other midengine cars such as Miurss Boxers, etc etc.