I find it hard to believe that the Ford Motor Company, or any other US car manufacturer, would offer up their original tooling to the highest bidder.
From my experience working in the manufacturing business, when a mold is no longer useable, it is destroyed, reworked, or it goes straight to the recycler.
From the looks of the replacement parts I have ordered, the parts are larger or smaller, contour lines do not match up, rounded as opposed to crisp lines, I think these suppliers took an original part and made a half hearted attempt at making a mold from that part and are now trying to pass it off a OEM.
I also find it hard to believe that Ford would sell their mold, knowing that it was worn or damaged, and let it be used by an unaffiliated supplier to continue to make money of of it and market it as OEM.
That just doesn't seem like a good business policy to me.
I don't think the replacement parts are being stamped out of vintage mustang dies and molds period.