Eric,
You have now experienced first-hand, "inaudible detonation" (some say it doesn't exist...). While you may not have heard the pistons getting beat up by too much compression/not enough octane, that ;s why there was piston pieces in the pan. We went through the same issue, going in to clean up oil leaks, in our '69 428 from the Catalina wagon. Found pieces of skirt in the pan. Never heard a lick of pinging.
In answer to your question, we always use Comp XE262H as a replacement cam for "stockish" Pontiacs. GREAT cam in a 389 with TriPower. Avoid the old 268H. That's a Magnum grind, with symetric lobes and "single pattern". XE262H is parametrically smilar, with all the modern features of the XE series. It works fine with stock valve train components. You can even use it as "non-adjustable" (base circle is same as stock cams).
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