I have 13s on mine. I dont remember what the size, maybe 155/80-13. None of my tires match and all but 1 need to be replaced before its ever driven, but I got a good kumho on it.
I plan on trying to get more original dunlop tires, and use the kumho on my spare. If a dunlop tire isnt available, I will try goodyear. Kumho is a good brand. Had them on my mustang and my husbands neon, but it just doesnt seem appropriate on a gt6... ...I dunno, maybe Im weird.
I should point out that I have wire wheels. If I had minilites, I may do something else. Steel wheels... ...I dunno