Welcome Guenther!
If there is no concession for allowing imported classic cars to retain their mph speedometers, then your best bet is to send a standard mph speedo to one of the U.S.-based instrument and gauge specialist restoration shops to have a kph overlay. The export kph speedos do pop up from time to time, but you might wait a few years for one, and then have to pay big $ to get it.
I have a 69 Camaro 200kph speedo and noted a thread over at a Team Camaro last year where a member sent his for restoration and authorised the restorer to digitise the graphics so they can make an appliqué to convert mph speedos to kph. I would expect that most if not all of the major players could offer a similar service to you for a 67.
You could try contacting Redline Gauges, Instrument Specialties and Bob's Speedometer to discuss options.
Let us know how you get on!
