Thanks. I've modified the original post after looking at my notes and some more internet searching to settle some conflicting info.

Best I can tell right now, since I apparently never got a copy of the J866 or J661, is that the temperatures I first posted with the Friction codes are a simplified interpretation. The 0-200/200-600 F can be found in articles from Motor Magazine and Hot Rod. The 0-250 F came from SHO Times and maybe other places.

But when you look at J661 test reports, its clear that not how the test is done. There are tests at increasing temperatures, then recovery after heating. The J866 codes use the results of the J661 to come up with the first letter which is 'Normal' and the second letter which represents 'Hot'.

As the Chase machine this testing has been done on is a drum, many argue it is not a particulalry good test for actual brakes. There have been ongoing attempts to come up with a more representative more repeatible US standard, but so far no dice. So it continues to be one of the few available means to compare lining materials.