Are your sure the clutch you took out was 11", not 10-3/4? The 10-3/4 was the heavy duty clutch up through about 1954 I believe. I went through a lot of confusion when trying to figure out what clutch was correct for my 1940. I thought it was 11", but eventually detemined that it was a 10-3/4. I would stay with whatever was on your 261. The 11" is available from local auto parts stores, but I had to order the 10-3/4 from one of the old chevy truck dealers.
Steve


See my 1940 Canadian GMC:
http://community.webshots.com/user/ndnchf