Cant think of any thing that has that pattern, could you be measuring it incorectly and it really is 5 on 5.5 inch. center of one hole, skip one and the center of the next, plus one quarter inch.
went back with the verneer calipers and did the side by side measurement. 3.23" stud spacing = 5.5" bolt circle. i need to not use a bent measuring tape in a dark garage. my bad. i thought that was a little queer you'd think after all these years i'd know better! i need to listen to that little voice that tells me when somethin' jus' aint right.....