I recently got a 66 thunderbird with a 390 that needs major rebuilding...like anyone, i am also looking for more horsepower...i was wondering if i should look into the 428 which is rated for 345 horsepower as apposed to 315 (in the 390), look into the more expensive route of a 427 with 2X4 Barrel rated at 425 horsepower, or finally just keep with the originals and modify it?