Help:  I'm installing new seat foam, new leather seat covers, and correct seat belts in my '70 coupe.  Problem is, the seat frames I have are from a ’74, so the backs don't have shoulder belts pass-through openings.  I can cut out the openings in the frames but I need the guide brackets that are spot welded around those openings in '70-'73 seat frames (circled in red in the photo).  I’m looking for an old or damaged seat back frame(s) with that bracket that I can remove and use as a pattern to fabricate sheet metal replacements.  Alternatively, does anyone know of a Corvette parts vendor that sells those guide brackets?  Thanks!