Im guessing you know more on the subject than I. I was not aware of that change. Do i have it wrong on the significant HP drop?
No. Sad to say, you got it right.
Starting in '71...compression ratios dropped, weaker cam specs, exhaust restrictions, parasitic air pumps, leaner mixtures, smaller valves, smaller and fewer carbs, etc., etc., etc., ad nauseam.
It was all bull$hit! Not hopeless though, heh heh. I showed 'em, I showed 'em good.
Shortly after the 2cd gen Mopar Hemi came out in '66, (street version, race version came out in '64), my entire life was devoted to getting one. Saved every penny I made and waited until I could get a drivers license, which would be in '73.
They discontinued the Hemi at the end of the '71 model year. I was teary-eyed for months.
A new plan was required. I ended up buying a new '73 'Cuda 340. Enjoyed driving it mostly as it was for a few years while gathering up Hemi parts.
Combine ingredients, stir, bake, drop the clutch, bang those gears.
And he spewed much exhaust and tire smoke into the air happily ever after.
PS Emissions wasn't the only issue that brought it all down, the insurance companies also helped screw it up. Tremendous premium increases on high horsepower was a real strain on the musclecar market. My opinion...Detroit changed the way they measured hp to lower the numbers and mitigate this situation.
By the time the insurance companies caught on, nothing had enough horsepower to worry about.