Jon G, thanks for the info.

I finally found it....the 1960 Rochester B, BC design changes (attached).
Low profile carburetor design used on trucks beginning in 1960.

Before I "bug out" I wanted to mention this for reference.
Because of the change to a wider (2-5/8") throat diameter (air cleaner mount), the 60's Rochester B requires adapter ring(s) to allow mounting a 1959 and older original air cleaner (2-5/16").
I don't have a YF3211S to look at but I suspect the same adapter(s) would be needed here as well.
Attachments
Design Changes 1960.jpg (228.54 KB, 211 downloads)

Last edited by buoymaker; 01/29/2021 9:54 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."