Let's put a mild 8.2:1 360 on the dyno.

stock hi compression Dart 340's were only 275 h.p. and with gears and a converter were very quick on the street.
..300 hp and 350 ft.lbs in a light A body is just fine!
275 was way under rated. That number was all buttoned up at the factory to meet the emission standards etc. and make the cars insurable. 275 at what RPM? Real numbers on these were 300-320.