FYI: The 261 CID engine was MFG first in 1953 for the (54 model year) and continued till late in 1962. This engine was used in large trucks/busses and others as a 'special order' too. Some were used in Pontiac autos sold in Canada as well.
The one in question could have been installed by someone other than the GM factory, or It's a 216 and the seller got the numbers transposed.
Check the casting #s in our "casting #s" section.
Good luck.
