I'm an AutoCAD Draftsman. If it were MY car, I'd do a rubbing of one of the existing stamped VIN's, scan it, import it into AutoCAD, trace it, and have an identical 1-Piece stamp made by one of the steel stamp makers.
I got a quote on a FoMoCo steel logo stamp like is on pulleys and stuff, and it was $65. I would guess a VIN stamp would be $150 or less.
Then you could experiment with ways to stamp it. A Hydraulic press would probably do it. The method Ford used allowed the characters to bulge out underneath like the backer was not steel. Maybe very hard rubber or plastic or wood.