Glad to see the Interceptor made the list, but no surprise that the earlier CV-8 didn't. No one ever seems to remember them, perhaps because they made so few. With a 700 lb. weight advantage over the Interceptor, the C-8 was the fastest 4 seater in existence in the mid 60s and fits the GT label even better than the Interceptor.
The other car I'd add, probably because I own it, and it is also of very limited production, was the Lamborghini 400 GT. Four wheel discs, all independent suspension, 4 cam V12 with more power than the competition, it was another great GT car, whether in the earlier versions or in the Islero model I own.
BTW, I have jumped into my Interceptor and driven 1100 miles in one shot (Tahoe to Vancouver BC), stopping only for gas, in around 14 hours straight. That's what I call a great GT car.
The MGC is a nice touring car, but not really in the same class as these.