67 Barracuda Speedometer Questions

This for a customer of mine he has exactly what your car has except no tachometer. He wants to go to 150 MPH speedometer gauge and would like to know if this was a factory option or can be retro fitted to fit his car. His current speedometer is locked up. So, if we can get a 150 MPH speedometer with trip odometer that has a screw on cable that is what he wants to do. If not, can I install this one in his current dash and just change the cable?

This was an old drag car put back on the street. The speedometer gear and cable have just been replaced by owner, but the current speedometer is locked up. So Now it is unhooked as to not ruin the gear or cable.