Might F 20 3 under the distributor (to the left, under the distributor?) be a block casting date? If so, it would be June 20th 1953?

Is the F 20 3 code in the ledge/boss in the block, to the left of where the distributor enters the block (as LONGBOX55 suspects)? If so, there should be more characters in the code.

Here are photos of where the various codes are found on the block.

The date above has been changed as per rednate's correction, below