Well, I'll reprint my email to Edelbrock Tech Dept:
"Gentlemen:
I have a Carter AVS carb which I'm trying to build up for a future project: '67 Chevy K/10 [half ton 4 x 4] Suburban with a 454 engine.
I understand Edelbrock now is marketing an AVS carburetor.
This carb is stamped K7 4966S. Inside, the metering rods are stamped 16-189, primary jets are 120-389, secondary are simply "489." [I think someone may have reversed the jets from their proper positions -- as the 489 jets are old Carter "high-types" to go with the 3-step metering rods that were peculiar to the Carter AVS system. Also the accelerator pump piston is brass with a purple (!) leather cup unlike the EDL 1470 nylon/rubber unit in the [AFB] Performer series. The pump piston spring is red, also. The step-up springs are plain but appear most like the purple springs from my AFB spring kit. This carb has a vacuum choke and a passenger-side EGR port (which I intend to delete. And I also intend to convert to manual choke.) It also has a hot idle compensator bi-metal vacuum leak inducer between the secondary venturies -- which I will also delete.
I measured the throttle bores with a vernier caliper: Primaries: 1.433~" Secondaries: 1.678~".
My questions are:
1] What Edelbrock Thunder carb is this closest to, so I can get a calibration kit for it?
2] What is the CFM?
3] Does Edelbrock make the 3-step metering rods and "High-type" jets for the AVS Carb system, or do I have to convert to the AFB system 2-step metering rods? ..."

Their answer:
"1) We have no way of knowing which AFB carburetor is closest to our carburetor. Their jets and rods went by a different numbering system than ours, which go by orifice size.
2) We do not have informantion on Carter carburetors.
3) we do not make a 3-step metering rod, only 2-step. Thanks. ..."

So I figured I lost his interest as soon as he realized I wasn't buying one of their shiny new spendy carbs. Also he wasn't paying attention since I was asking about the AVS carb not the AFB. Clearly "AFB" is a bad word in their Company vocabulary. "Performer" is the good word.
To us old hotrodders one aluminum four barrel is pretty much like another on paper. But aparently appearances can be deceiving.

I read Dave Emanuel's book, "Super Tuning and Modifying Carter Caburetors," and thought I saw something in there about how the 3-step rod was a good idea for mid-range performance -- like in towing.
Since I intend to build my 454 to tow a 20' camp trailer, this seemed like a good idea. Finding someone with the technical chops to machine a custom pair of 3-step rods will be the difficult part.
Sorry for the long rant.
Can you, Carb King, answer my first and second questions?
Thanks.

Every 25 years I like to rebuild that 292 just for GP