I don't recall ever having that problem; what I noticed was that clip-on weights on the inside of Ford 14x7s would hit the edge of the '68-'70 Mopar upper control arm. Those were drum brake cars.
You could try a 1/4" spacer ring; any thicker than that and there's not much thread engagement on stock studs.
If you use spacers and their holes are too big to be captured by the studs (meaning they move around on the drum), a few dabs of weatherstrip adhesive will hold them in place.
Should be a good market for 15x8s, as they fit the '68-later Bs fine.