5 x 4" with 1/2" studs

[billd]

I have a pair of brake drums 10" x 2-1/2" with 5 x 4" bolt circle with holes for 1/2" studs instead of the normal 7/16". Any idea what these are for Hemi SS?

 

[6pk2goDemon]

The 1/2" opening in the drum is for the shank of the 7/16" wheel stud.