old colonel,
I suggest you talk to an engraver(Erik Boessler did this type work, between guns, before he passed away).If the cost is too much,maybe he would engrave enough cases cheaper.An alternate would be to talk to a machinist about making a jig to use standard number/letter stamps. The jig would have to "locate" the stamp and "index"the case.Such a jig would be very slow, but would be very adaptable for differing headstamps.
Mike