My 283 is a 66-67. It has 3896944 cast numbers @ the driver's side rear of the block. When you clean it up & re-gasket everything, I recommend replacing the timing chain & gears while you're at it. You don't know how many miles are on it and SBC engines might get 100,000 miles out of an O.E.M. set if it's not worked too hard. Also, replace the oil pump! 283's are tough little engines that love to run! Not overly powerful, but reliable as an anvil!