I got the correlation.

I took the SD over to Dieselnut14's place over in Sea Cliff.

The SD is set perfectly at 15° ATDC using the RIV device.

The pulse timing device showed 13.5° BTDC.

At the NJ GTG, he measured six different vehicles, all with 616 and 617 engines. The highest reading was 12° and the lowest was 6°. Clearly, everyone was running with late timing.

So, my best estimate of the proper timing with the pulse device is just about 14° BTDC.