I need some help understanding the numbers/letters stamped on my 455 block. I was told the engine is not original to the car and was a rebuild. I did some searching on this forum and I still can't figure it out. I just want to know what year the engine was built. I can't get to the numbers below the distributor unless someone has some ideas. Thanks!

 

I can tell you the heads are 1970. Looks like the block stamp is maybe a marine application? I'm sure the experts will chime in.

 

The drill mark on the pad is supposed to indicate marine or irrigation pump motor