Actually the 261's had two sets of captain bars. The one you mentioned and another one on the other side of the engine behind the exhaust manifold. There is a good tech. article on the 261 at Jim Carter Classic truck parts, which discusses the 261. Here's the link: http://www.oldchevytrucks.com/cgi/htmlos.exe/002315.2.3011496932800016126

Here is a picture that shows the other location of the second captain bar on the 261 engine I am in the process of rebuilding:
http://community.webshots.com/photo/109150147/114347164LlduFw

Jim