I'd keep adjusting the timing until the ping is gone, or nearly so. A little bit of slight ping once in a while you could most likely live with. After you have the timing set where it works check the numbers. 22 is fairly low, but with the cam change you are not dealing with a stock engine.

It is, as mentioned above, imperative that you confirm your timing mark on the damper is at top dead center. Use a piston stop to aid in making sure it is where it's supposed to be. If not all those numbers don't mean a thing.

Also, as mentioned above, a lean mixture and high heat will increase the chance of detonation. Do you have a stock jetted carburetor, do you have a good fuel pump, is the float bowl emptying when you mat the gas pedal?

You have a pretty stock build except for the camshaft. If you get the timing set to a point where the detonation stops and the engine idles and runs normal, who cares what the numbers are? Just drive it. If you get the timing set to a point where the detonation stops but will not idle or cruise with that timing you most likely have a component problem. All things point to the camshaft if the rest is stock.

Your camshaft should have came with a cam card showing all the specs. One of the specs will be the point at which the intake and exhaust valves open and close. Check that with the specs of the stock Pontiac camshafts. The Pontiac engineers where smart guys and they designed camshafts that worked well in the Pontiac engines. Of course as mentioned earlier they also had the advantage of good leaded gasoline, the kind I used to buy for $0.25 a gallon. Pontiac engineers designed camshafts for Pontiac engines and did a better job of it than Comp Cams could ever hope to. If your cylinder pressure and dynamic compression ratio is too high with the Comp camshaft, maybe look into getting one closer to stock. If your engine was made with a 68 camshaft maybe a 67 or 66 will work well with the crappy gasoline you're forced to buy. I'm sure Melling still makes stock spec camshafts, they made the one that your engine came with from factory.

Pontiac engineers generally .designed camshafts with a fairly wide lobe separation angle and intake centerlline of around 112-113 with a few exceptions. Aftermarket grinders such as Comp Cams stray from that. Seems like Comp likes to suggest camshafts that make horsepower at high rpm range and don't worry much about torque. What works for a small block cheby isn't going to work in a Pontiac engine. Pontiac engines are made with more low end torque and usually make their power at a lower rpm.