You have probably read this already but....
http://www.wilwood.org/PolyMatrix%20Catalog.pdf
The D compound starts to loose it at 600 which really isn't all that hot. It you are happy with your balance currently (bias bar centered?) then I would probably go with the J pad for the track. They are good over 1300, have a very, very flat torque curve, will actually stop better than the D pad when cold and the are closest to the CF of the pad you are running now. Even so if you are happy with your front to rear balance the CF of the J pad is still more than 10% higher than the D so you will end up dialing in a little rearward bias. Added plus is your peddle effort will be reduced.
The A, B or C compounds work temperature wise but the torque curves are not as flat, the CF can be significantly higher and they don't work as well cold as the J compound. These are all dusty compounds. And I do mean dusty!
Porterfield make great pads as well (Roscoe sure loves them). I would probably not use the R4-S since it has a lower CF (more peddle effort) and I am not sure of its temp range. The R4 would be good for the big tracks but it optimum range is over 450 so you concern about warm up at the SCCA event may be an issue. The newer R4-1 looks very interesting. I would love to see a temp/CF chart from porterfield. Wish they published one.
NOW GO GET THAT PORSCHE!!!
Rick