Al, those dimension don't seem
exactly right. If the bolt-hole mounting circle is 3.25 inches, with 9 holes, the center-to-center spacing on the holes should be 1.112 inches.
But, if the bolt hole center-to-center spacing is 1.25 inches, then the bolt-hole circle diameter should be 3.65 inches.
ref
http://www.motoredbikes.com/showthread.php?t=30309