There was a place on State Street and it seems like between 17th South and 35th South, east side of the road. Something Electric.....Sorry but it's been quite a few years but thats the place that did tachs, speedometers ect when I was in business.
They calibrated and with cable speedometers, put in the correct adaptor to compensate. Adaptor screwed onto the trans, cable screwed into the adaptor.
I don't know if they are still there and can't remember the name.