My 81 has an 85mph speedometer. Does anyone know if the speedometers from later 1st gen RX7s can be swapped into this car? Has anyone put an aftermarket speedometer into their car?

 

I have a 1980 that came with the 85 MPH speedo and have replaced it several times with speedos from a '79 and from later 80's models.

Once you remove the cluster there's only 2 screws holding the speedo in place.

It's a pretty simple job.