I found yet another official GM source (see attached) that confirms the fuel inlet nut on my 7028212 Rochester 4MV (4 barrell) carburetor as being correct...the photo of my carb was in my opening thread on May 15, 2012. My fuel inlet nut is the same as the one in the attached GM document, the photo that Jeff68 posted in this thread on May 16, 2012, and the photo that you posted in this thread on May 22, 2012. The attached GM documentation supports the other three GM documents that I posted in this thread on May 17, 2012.
-Exploded view of a Rochester Carburetor Model 4MV (327 & 350 cubic inch engines) Float Bowl, Figure 35R on Page 6M-20, from a "1968 Chevrolet, Chevelle, Camaro, Chevy II and Corvette Chassis Overhaul Manual. (dated 1967)" Illustration #11.
In relation to your last comment about the fast idle cam (aka "kickdown lever"), the attached document shows it looking like the plastic version, not the metal one.