You can swap the tailshaft housing for one from an older TH700R4, with a mechanical speedo drive. Then you may need a custom-made cable with the correct ends, I do not remember what kind of cable I had used on mine. Changing the tailshaft housing also makes it easy to change the driven/drive gear, so that the speedo is correct.
No electronics, OEM simplicity and reliability.

Last edited by wave1957; 01/18/2021 10:42 AM.

'57 Chevy Suburban; '70 Chevy Impala.