Buoymaker - you listed the venturi size for the Carter 9400s, but there are smaller Carter AFB carbs.
The smallest one I could remember without doing a bunch of research does have the dimensions I mentioned, same as the Holley 390.
As I stated earlier, I have not used the Carter on a 235, but did use the 9400s on a 300 CID Ford six replacing the original Holley 1-barrel.
There was a significant difference in power; but the biggest difference was fuel economy, especially on the highway. The AFB gave a HUGE increase in fuel economy over the Holley. However, I will admit to knowing more about tuning the AFB than the Holley. Possibly one reason I had no low RPM issues was a 4-speed with a "granny" low gear.
I won't post the fuel economy but this was in an extended wheelbase 1979 Econoline with a stock fuel tank. Loaded for a swap meet, we drove the speed limit, maybe a tad over
(55~70 in Missouri, 75 in Oklahoma) from Eldon, Missouri to Chickasha, Oklahoma without stopping for gasoline, and I have a witness.
Again, this was a different six.
And if anyone wants to fabricate an intake so they can use the Pontiac Sprint Q-Jet, and cannot find one, give me a call
I have about 2 dozen of them. But unless one is grounded in intake manifold design, I would not recommend one of these.
Best would be a slightly larger single barrel, on three MUCH SMALLER single barrels