But there is still the problem of market-specific emissions compliance and fuel quality or type... which is why there is now the voluntary SAE J1349 standard which requires a certain fuel type, the proper "operating" oil level and tighter control of temperatures... as under SAE standards, you can still gain 5-15 hp from running lower oil levels or thinner oil and/or running higher octane fuels.
And even then, you can't be sure whether the numbers quoted are for the local car or for other markets, as local dealerships don't actually have the equipment to test engines but rely on estimates from the plant. Sometimes rough estimates, as some engines are detuned for the local market in deference to the quality of the fuel we have here.
Thus... the only really telling number is trap speed in the quarter mile... because you can't fake that. 