Aside from looking really cool, duals have some real advantages in carbureted applications. Cylinders burn an air/fuel mixture. Ideally, the fuel is completely atomized as it enters the cylinder. Anything that causes atomized fuel to drop out of the mixture and "pool" is really undesirable.
Fuel is atomized in the carburetor, and the change of state from a liquid to a vapor actually has a sensible cooling effect. Coler temperatures cause vapors to condense. The higher the intake manifold temperature (after the fuel is atomized), the better chance the fuel has of remaining vaporized.
In a dual carb application-- the intakes sit right on top of the really hot heads, and they pick up a lot of the heat. The intake runners are short, and pretty toasty. Tehy get hot enough that in some applications, guys will use a phenolic, non heat-conducting insulator between the intake (where heat is good), and the carb (where it's not so good).
With duals, the intake length is identical on all 4 cylinders and that length is more appropriately tuned to match the engine's power range. There are a lot of advantages.
In a single carb configuration-- it's a L O N G way from the throttle plates to the intake valves, and there's a lot of chance for the fuel to drop out of suspension. As I mentioned, the change of state of liquid fuel to vapor actually refrigerates the intake as well. Without heat from the heads, intake manifold icing is a big problem.
VW had the funky cross-over tube to keep the intake manifold from icing up. No decent sized exhaust has 'em. The EMPI 1-3/8" headers have provision for them... but the way they are constructed, they don't work most of the time.
It is hypothetically possible to have a bigger header fabricated with the provision for heat risers. While you are at it, you'll need to fabricate an entire intake system to match up to it. Don't forget that every stroker engine combination is a different width.
In an EFI engine, all of these issues with a single throttle body don't matter, because the fuel isn't injected until it's almost at the intake port (ideally). Actually, it actually works better with a single TB, because there is nothing to synchronize. But as Gordon pointed out, the existing end bells are pretty inadequate for 2L+ engines (from a flow standpoint).
The existing end-bells are the cat's meow on an injected, turbo motor, as the size doesn't really matter (the intake charge is under pressure).
So... in other words, the single-carb thing has been tried. It's a lot of work to get it to work right. When it does, it's really only fit for smaller engines. If you want to do that, I'd just get a modified Mexican Beetle injection system running MegaSquirt.
Duals really aren't that hard in comparison, and they make a LOT more power for the same amount of work. They're actually pretty hard to beat.
I'm going to miss some spectacular weather this weekend and I am not happy about it.
