Speedo PPM

I have an 89 Astro that I'm installing a Dakota Digital signal generator on to the speedo drive on the transmission.
Trans went out, so I replaced it with a new one which had a cable speedo instead of a VSS.

Dakota digital makes a generator and a programmable signal interface for the speedo. I need to know how many PPM the 89 Astro requires to drive the speedo.

Anybody have any idea?

Thanks

4,000 pulses per mile. That also depends upon whether there was a VSS buffer module on your '89 (yellow plastic box on the ECM).