[olredalert]

-------Ohh yeah!,,,,,,,Your in my pond now. 421s continued all the way thru 66. In 67 Pontiac went to 400s and 428s. The 400s and 428s were just 30 over 389s and 421s. SDs stopped production at the end of 63 model year. The biggest available pontiac motor in 1964 was the famous (as opposed to infamous SDs) 421HO tri-power. It was rated 370hp in 1964 and I believe 376hp in 1965 and 1966. Im not aware of any differences in the three years with the exception of exhaust manifolds which actually may account for the 6 horsies.
-------Since Firebirds came along in 1967 and they were not a full bodied car the biggest engine available was a 400. Not up on horsepower ratings in the Birdies.
-------There was never a 426 Pontiac production motor that I am aware of. It is at least possible that 428s were really only 426 cubic inches and Pontiac didnt want to advertise engines of the same displacement as other divisions (427 chebbies) as well as completeley different companies, (426 wedges and HEMIs, and 427 fords and Mercs).
-------There were actually 4 421s available in 1964. Base 421 was low horse single 4-barrel. Then came low horse tri-power. Then came high horse 4-barrel, and finally the high horse tri-power which was referred to as the HO. This array of engine options was similar in other years (1963/65/66). This does not address any of the 389s which were also potent for thier size.
-------Lightest weight big body car was undoubtably the 63 Catalina swiss-cheese cars. Not only did they have a bunch of aluminum mostly at the front of the car, but they had drilled frames that Poncho nuts now refer to as swiss-cheese cars.
-------What an era!!! I would love to live it all over again..........Bill S