Bowtietim has that setup. See if you can get him on the website.
rgie,
I think that bowtietim has a 1954 261.
He'll let you know the years of his head and rocker arm assembly.
The 261 and the 235 had a least 3 different kinds of head/rocker-arm plumbing between 54 and 63, as shown at the link in my post above. And, I think the "848" head and rocker arms assembly had at least two different kinds of plumbing. I think you will need to know the adaptation needed for the year of your block to the year of your head (and maybe of your rocker arm assembly).
Let
Pre '68 Dave know the year of your 261 and he will move you along.
