69 Camaro alt,dist,carb question

[DSYenko]

Hi fellas got a 69 Camaro im restoring,has the 300/350 engine.Casting date L 10 8 and assembly date 1212.Just wondering if stuff like the alt,carb and distributor are normally dated BEFORE the assembly date or can they be inbetween the engine assembly date and the car build date?I guess what im asking is how complete is the engine on the date that is stamped as the assembly date? The distributor is dated several months before the block was even cast but im assuming it is the original.The carb is the only thing missing that i have to worry about dates on but im just curious.Thanks