[cycleguy55]

Ford Times August 1965: 427 CID 425 HP (street tune)
Car and Driver November 1965: 427 CID, 485 HP @ 6500 RPM, 480 lbs-ft @ 3500 RPM
Car and Driver April 1981: 427 CID, 475 HP @ 6500 RPM
Car and Driver April 1981: 428 CID, 355 HP

I'm not 100% sure of the C&D figures from November 1985, the scanned copy I have is hard to read.