pinging on an hill?

The Mopar Perfromance distributor is a good value. It has a fully adjustable mechnical and vacuum advance.

By pulling the initial back to 9 degrees you are right where you need to be (32 degrees) for total on a sb with magnum heads. As I stated before the magnum head is more efficient of a design than the old LA open chamber head so it does not require as much total timing. The new LS engines for GM are running less than 30 degrees total.

Before mucking with the carb you need to get the timing dialed in. Depending on your cam you could need as much as 20 degrees initial for clean idle and crisp throttle reponse on the bottom end. This will require an adjustable distributor or a lot of trial an error welding slots in a factory one.

Unless you have very low vacuum it is very seldom that the power valve needs to be changed. FWIW, the PV rating doesn't change the amount of fuel it changes when it opens.