Ok, took one off and went to the shop and got 12 standard bolts. I'm gonna put on my new wheels this weekend. I expect the bigger centercaps to come next week. Then I'll be set!

PS - the bolts are 10mm diameter (not sure of threads) x 30mm length with a 5/16" hex head. They're not too hard to get off, but you need a second lever to prop in the hubs to keep them from spinning.