figuring out advance timing

RRR.
Uh no, actually. My 66 GTO was rated at 10.75 CR. 1966 440 had 10.1 CR.
By 1970, the 440 Magnum was 9.7 CR, Pontiac 10.5 CR.
Pontiac used the 400 cu in engine as the high power engine in their line up, giving up lot of cubes to the other brands. A silly decision, in light of how things panned out. I am NOT a Pontiac fan as such, just always like the look of the 66 GTO. If the 66 had not been made, I would have bought a 68 Charger that was offered to me.....