As stated above, the "captain's bars" are not a sure indicator of a 261, especially in 1954.

As stated in a Jim Carter Tech Tip:

"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. See photos below. 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."


The best identifiers are the casting numbers (linked above).