Pinging should not be an issue at around 9-1 compression ratio. If you do get ping, a little modification to the timing curve should cure it. The reason I suggest a CR increase, is it will give a power/torque increase across the complete rpm range.
In general slant six engines had a little less the 8-1 CR from the factory (regardless of what the books say).
A cam change will (in general) have more effect in a particular narrower rpm range, and with a low compression engine, actually hurt torque, in the range where you want it.
The best way would be to raise the compression, and then match the cam to your requirements. Then play with ignition curve to really optimize everything.
PS: I hope you are running electronic ignition (but not the "lean burn").

LOL, it's ok. Ya don't know me, so there's no way you'd know. My 65 PW uses an old MSD6C box, because I didn't like the lack of power from the standard Chrysler electronic ignition ( I converted from points before I started the engine for the first time). If I can find them, I run non-resistor plugs, metal conductor wires, and a high output coil. I like LOTSA spark

Can someone tell me any idea how much has to be shaved to get the CR up to 9:1?

I would opt for spiral wouund magnetic suppresion wires, espicially if you are going to add electronics (megasqirt). You will still have good spark and no RFI (neighbors will love you for it).

You have to measure how far the piston is down the bore, the thickness of the head gasket you will be using, and the size of the combustion chambers. Then you can use the calculator, to determine what size chambers you need to get the ratio you want, and "IF" that difference is like 9 cc's then you remove .0066 from the head per cc difference or roughly .059

PBM, the parent company of Erson, will be at the PRI show on the 9th-11th of Dec. I will be there, also, and will make a point of talking with them.