Good that you read not to install a Weber 38/38. Not because it is a bad carb, I’ve ran them for over a decade and not once have I had a single issue. That said, the 32/36 AND 38/38 were made for engines no bigger than 2.3 liters. The accelerator pump shot is not sufficient for an engine bigger than 2.3l, and a lean sag will be experienced that can not be tuned out. This is why many claim that Webers like lots of advance, which is hog wash. The extra advance is helping a very lean air/fuel mix to better combust, that is all. Also, most end up jetting the idle circuit pig rich to compensate as well.
A 4 barrel is not too much carb for the 2F. The primary’s on a 4 barrel are smaller than a Weber 38/38 and Holley 350, and the secondaries will only open when a restriction is present. At least, if you are running vacuum secondaries. CFM calculators should be thrown out the window when sizing a carb for a straight six. The intake stroke pulses the carb, this can be seen when running multiple carbs where each throat feeds it’s own cylinder. The 2F requires 700 cc’s to be filled per intake stroke, a Chevy 350 requires 712. At any given rpm it takes the same amount of time and volume to fill the 4.2 l6 as it does the 5.7 v8. Therefore if a v8 of similar cylinder volume requires or runs best with a 600-650 cfm carb, the same can be said for the l6.
This has been shown with 650-750 cfm carbs on Ford 300s and also Chevy 292s. If using an “average” cfm calculator on a straight six, your cfm will show you need a much smaller carb and will become a restriction to the engine.
All that said, if no change is made to the cylinder head and exhaust, and the restriction occurs elsewhere, any benefit from the larger carb will be greatly reduced.
Anyway, I do believe Offy will still make the C series manifold upon demand. They are listed on Summit Racing, and have a ship date so…….
Lastly, the C series specifically states to run a 500+ cfm carb. The DP states 500cfm or less.