A bushing/spacer might work if you finished the inner diameter of the bushing/spacer and left the OD .020" or so big, press it on to the cam, dowel it in place with a couple of dowels so it doesnt move, then chuck it in a lathe with a steady rest on the next closest cam journal and then finish machine the bushing/spacer OD, that would make your bushing/spacer concentric with the others, might work