The swap went very well. I've been driving it everywhere for 18mo. The speedo started bouncing for a few weeks then it quit.
I replaced the sensor in the rear diff just because it was easy. That didn't fix it.
I can either:
1. go through the headache of converting the wiring for the 95 cluster I have not knowing if that will fix it
2. Install a Summit or similar GPS speedo
3. Find the speed sensor on the GM trans (4l60e) and install a compatible speedo
4. some other solution I haven't thought of
What would you do ?

 

Volvo 960 service & repair manual is a good resource to start with. This shows the ABS set up including the rear diff speed sensor. Was the speedo working prior to the swap?

 

Yes, speedo worked prior to and after the swap. Thanks for the link