Distributor recurve

I'm rebuilding the distributor on my car to adjust the timing advance. My driving is mostly at lower RPM, almost never above 3000. What is a good starting point for total mechanical and vacuum advance on this build?

- 1974 Dart with 904 transmission and 2.71 differential
- 225, rebuilt with 8.9:1 static compression and Oregon 2106r camshaft (7.7:1 dynamic compression)
- Super Six intake manifold
- Carter BBD clone 2bbl carburetor

The original distributor is in good shape. It has a 15R governor and 8.5R vacuum pod. I also have the distributor from the Super Six donor car (a 79 Lebaron), which is a bit corroded due to being left outside with the cap off. It has a 9R governor and a 11R vacuum pod. I also have a set of different mechanical advance springs for adjusting the advance rate. I do not have a distributor test machine.

The engine seems to like a lot of advance at idle (it runs great up to 20 degrees BTDC), but pings at higher speeds under load. That's in large part due to the mixture being lean when the throttle is open (according to a wideband AFR gauge), but also partly due to timing.

My plan (unless I get advice to the contrary) is to use the original distributor, but with the Super Six governor and vacuum pod. Any thoughts?