The 1955 (Racer Brown) article has no information at all about installing a 235 head on a 261 except this: "A head from any 1953 or later 235 cubic inch engine is completely interchangeable with the 261 head". The only reason they used a 235 head is that the chamber volume is smaller, which requires less milling to achieve a specific compression ratio increase.
No mention of steam holes, bolt tightening sequence, or gasket difference.
