Remember when the Grand National was mfg, Im willing to bet that hp rating was so that owners could get them insured, insurance companies made their own rules at that time and didnt have much govt. oversight (even though we've been told thats changed now it still doesnt seem like it). Those cars also had a reputation for being tuned from the factory on the mild side and didnt take a lot of effort to increase the output. If you ever read the Grand Nat. history youll find that not all cars with that engine package were mfg as Grand Nationals, the eng could be ordered in any Buick Regal and the eng package was available as early as 1978. At one point in the mid 80's the FBI ordered 75 specially equipt GN's that were rumored to boast 370 hp and run up to 140+ mph. I wonder where those cars disapeared to.