That setup was sold back at the turn of the century with 48DCOEs and it  worked as well as a Holley 4bbl- a bit more expensive and a bit more tuneable. It also fit under a stock engine screen. One of our So-Cal friends used one for years- he called his candy-apple-red Pantera  'Edible Red'. Don't remember what intake was used.

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The rig ran fine on his modified engine, but for a 351-C engine, it needs 50 or 52 DCOEs. Wilkinson's dual-Magnecharger setup used 50DCOEs. Faux-Webers are available from places that cater to off-road VWs and Sand Drag buggies, up to (I think) 58 mm- the size Shelby used on a few of his 7-liter Cobras.. Not sure if the shop is still around anymore-its been awhile since I heard from them.

That set up is approximately equal to a Holley 1850 600cfm carb.

The difference is that with the Webers you will be idling on all four throats all of the time and on the Holley only the front two.

There will be differences in the throttle response and count on the Webers to idle much heavier then the single Holley.

Where it would make a big difference is if you were running two of those setups on a dual four barrel intake manifold.

So my opinion is that Weber setup is more for looks then performance.

IF you were interested in the best balance/compromise in caburetors on a Cleveland, then you would want to run a dual four barrel Holley intake manifold with two vacuum secondary 600 cfm carbs with progressive mechanical linkage.

There the engine would run on only two barrels up to the 3,000-3,500 rpm range, then start to open mechanically the primaries on the second carb.

The vacuum secondaries would open on their own by engine demand.

You want a 180° designed intake, not an open plenum intake like the Ford experimental dual four or three two manifold was. That is a single open plenum with a changeable top. Today we would describe it as more of a "blower" intake.

What would make that set up work really well as a driver is the design of the intake manifold. There are several key elements in it working well and the manifold itself is really the biggest one.

So what that system would offer would be the maximum usable carburetion on a 351-c and best economy around town with a very noticeable throttle response increase very similar to running a IR 48IDA Weber set up. It would also give greater tunability throughout the rpm range of the engine then one single 4v carb could.

The problem is there is no intake manifold ever made for it for a Cleveland.

There were for the 289-302's, Boss 302, FE's and the 429's though. So this is all theoretical for a Cleveland and would be extra challenging to accomplish in a Pantera.

There was a 351W dual four Holley intake made by Price Performance resembling the design of the Ford 289 dual four and C60A Ford dual Holley four barrel "Trans-Am" intake. The Price flowed around 285cfm on the intakes so it would work on the Cleveland with adapter plates and milling off of the thermostat housing but it was made in very small quantities and there is no longer any new stock left of them. So in practical sense, it is obsolete.

Stock Boss 302/351C iron heads flow around 250cfm unported. So that is a good match for them if you can find one and put the work in to modify it to the Cleveland.

It would take a bit of mill work to make it a Cleveland intake but it is possible but translate that into fairly expensive and it is unknown what the physical complications it would have to make it fit into a Pantera  because of the space limitations caused by the decklid.

I had looked at it but never quite got there. The Weber setup I was already experienced with and it just so happened that I already had one sitting on the shelf so the answer to why and how it happened for me is kind of obvious.

So really this is all theoretical. The best practical solution left is an EFI  conversion since the compromises there are the minimalist that is ever going to happen in out lifetimes.

The new Holley Sniper for a single four barrel application runs very well out of the box with no need to do any tuning to it since it is self learning. You just need to be patient with it as the CPU does it's thing and brings all readings into the optimum categories as you drive it.

It will have the best combinations of clean idle, fuel economy  and maximum HP and TQ. It is essentially, plug and play.

It's shortcomings are largely that it lacks an exotic look to it like the multiple carbs do.