Just measured with tire off. Corrected size is 13 x 11.5", but look at anything close. I tried posting in the Monposto section, but did noy get a response. I have a vintage FB car that the PO had an off course excursion and cracked both rear wheels. The bolt pattern is 4 x 4.5". Pictures in the thread below. If you have or know of someone that might have somthing similar, please let me know. Thanks.
http://www.apexspeed.com/forums/showthread.php?t=28488