I know that the years you want are 63-67. There were three different 427's, but not sure if all three of the 427's came out in 1963. You have your L36 which pushes 390 horses, then is you L68 400 horses and last is your L71 pushing 430-5 horses. All these are 427 blocks. The engine block L68 and L71 are tri-carbs