What you have now looks awful stout for a "A" body as is. Not sure where your final compression ratio will be as far as pump gas? But keep in mind, 400/425 hp in a "A" body is as much or more then is needed for a crazy fast street car.
My 64 valiant with 408 has a 580 HP so I'm spoiled. Just put the alterkation and street Linx on this coronet and it needs 600HP. What a great suspension upgrade.