Olds 455 engine

For BadBird67:

You have a Olds 455 engine. I have just bought a 1969 Oldsmobile with a 455 engine, casting number 396021Fa. I believe this casting number is for 1972-76 engines, but I'm not sure.

Can you help me in determining the year of this engine? Other info on the block is:

CFO 394 246 201

C 15 GM

Thanks so much for the help.

BuddyB