A quote from "The Forgotten 261" in "Tech Tips" from the menu to the left:
"Watch for the 'Captain's Bars!' The 261 has two pairs of parallel raised 3/4 inch long bars cast in the block. This is not seen on a 235 except 1954. One pair is above the starter and the second pair is at the top middle of the left side of the block very close to the head. ... The one exception is the early 261 produced in 1954 to mid 1955. It has only one "Captain Bar" above the starter but keeps the pair on the left side."
However, I have two 1954 261 blocks; one has both Captain's bars, one set above the starter and the other set on the opposite side, between the two core plugs and about two inches below the cylinder head deck. The other 1954 261 does not have any Captain's bars; it also has a casting number that belongs to a 235 block, according to the published guides. Both of these blocks were replacement blocks.
The "real" casting number is located on the forward part of the block; for the 1954 blocks it is forward of the fuel pump and just above the oil pan flange. On a used engine this area is usually covered with crud that must be scraped off to see the numbers. The later engines have the casting number forward and slightly lower than the distributor.
The only useful information in the "casting numbers" behind the starter is just the date code, for example: "E74" = May 7, 1954.
The numbers which may or not be stamped (not cast) into the distributor may or may not contain useful identification information. Sometimes it is a serial number, but not always. Sometimes it is blank, usually meaning that the block was purchased new as a replacement and the owner never bothered to stamp the apprporiate number on the pad.
A search on "casting numbers" etc. in this forum or in The Stovebolt Page will provide lots of information, both helpful and confusing.
Example of helpful thread.
