Interestingly, the Pontiac GTO of that period was a heavier car with the same motor. GM policy at that time was to limit their cars to 10 LBS/HP so the GTO had more listed HP.

Years ago my brother took my/his TA into his mechanic for service who found that the 4-barrel carb had a mechanical stop that wouldn't allow the throttle plate to open fully, thus limiting HP to 'the policy'. He removed the stop & voila - more HP.

And here I drove it for years without a fully capable motor, damn!

TAM