Tracking down my original bb 396 block

[chevyman0429]

Well I've decided to try and track down the original blocks for one or all of my 69 ss chevelles. I have 2 Fremont built cars and one from Kansas. Is there anyway to determine where the motors might have been built off of where the cars were built. I mean is there any specific plant that might have built motors for specific plants that built the cars. Also what time frame would be expected between the time the motor was built verses when the car was built. I'm really hoping to find the original block for my 69 ss 300 deluxe hardtop. But also looking for the block for what I believe is an original 375 horse car. Any help would be greatly appreciated.