Carter and Holley are both "square bore carbs" 9both primary and secondary bores are the same size so each corner looks like any other corner), they differ on the bolt pattern used to secure the carb to the manifold. Edelbrock clones of the Carter AVS have both bolt patterns bored into the carb flange. After market intake manifolds also have both Holley and Carter bolt patterns to mount either carb on top.
A "spread bore" Rochester Quadrajet (to further confuse the issue Carter and Holley also make a QuadraJet spread bore carb) that will not bolt onto a square bore manifold. The secondary throttle blades won't go into the rear holes in the manifold because they are as big as "barn doors". Because of this it takes about an inch thick spacer to adapt a spread bore carb to a square bore manifold or "vice versa
" (vice versa
is Latin for interchangeable). Because a BBC is two inches taller than a SBC you have two inches of free room to grow to install a taller intake (high rise) or an adapter plate without too much worry.
1966 was the last year that a Carter AVS or AFB carbs appeared on a production car. Staring in 1965 GM introduced the Rochester Quadrajet to replace all previous four barrels (Carter and Rochester). It didn't work out as a total replacement because Dontov and other GM performance engineers insisted that the Holley be used on their high performance engines (Z/28, and SS big blocks). Just as well because the Rochester plant couldn't produce enough QuadraJets to meet GM demand which is why Carter started making them under GM license to meet production demand (they where labled Carter on the throttle body). Holey made their 4165 spread bore carb to compete with GM as it was a spread bore with all of the tuneability of a Holley (it wasn't called a QuadraJet as that is a GM trade name).
Holley made a similar spread bore model carb in 850 cfm for big block applications.
Finally I will conclude repeating that no carburetor brand has a "distinctive" performance advantage over any other brand. A 650 cfm carb made by anyone will put as much gas and air into an engine as any one else's carb. It is the cfm rating (the measure ofthe volume of air that can pass through a carb's venturi that determines this size rating) that limits maximum horsepower.
Why Holley or Carter or Rochester or Weber differ is in the ability of the air fuel mixture to be tuned to your driving style, cam and head choices.
With a Weber you can modify every thing in the carb. It is why they demand the top price in carbs and people without a budget put them on their imported race cars from Italy, Germany, or England. The Holley is the next easiest to tune having only the boosters and throttle bores fixed; everything else can be changed to suit your needs and it can be done in a sandy pit area. Carter has fewer modifiable parts which helps keep a lot of "carb experts" out of trouble, but it is still light years ahead of GM. Rochester chose to make hardly anything adjustable (you change things by changing springs, or bending rods on the out side with main circuit enrichment circuits limited to a few different metering rods). Once set up it will run like that for hundreds of thousand trouble free miles. You just can't change anything on the engine without a professional retuning your carb.