360 Idle Quality

Got it, thank you.

So does it seem surprising that I can run 48 degrees of total timing and have no detonation issues? Does low dynamic compression and aluminum heads allow for that much advance?
You don’t have 48 deg of total. Any number of degrees of timing added with vacuum advance (either manifold or ported) goes away when manifold vacuum drops (IE you’re on the throttle). It is completely reasonable to have as much as 48 or 50 degrees at cruise when vacuum is high. And no you won’t see detonation there.