Hi Dan!
True, it is not easy to get american brand
oil in Europe - had the same question 3 years ago too. Got lots of response and after reading i had no idea what to use cause auf the different opinions.
I use Valvoline VR1 Racing 20W50 at my Roush 427R - no problems till now and easy to get in Europe (and the price is ok too)
Wish you a great day and much fun with your Cobra!
Greetings from Austria
Peter