This is a great thread to hold both the RNS-810 pinouts and the J523 pinouts so that OEMpl.us or someone else can make the wire which would allow the exchange of these units.
Here are the pinouts for J523:
T32C (the green connector)
The DIN standard VW audio connectors next to the fuse on the lower right hand side:
The overall view of the back of J523