I'm trying to convince Offy to mod their casting, to accept IDF Webbers. This should be more desirable than antique, Rochester 2bbl's ?  Any interest out there ?  Thanks, art.

Nearly anything is more desirable than Rochester 2bbls.

The younger crowd don't care about Webers. Instead, they buy used motorcycle carbs on eBay.

But the future isn't carbs, it's throttle bodies (for EFI).

The dual 2bbl Offy is NOT your first choice for performance.  It is for looks only.  Nearly anyone who uses that intake wants the look of two Rochesters or (better yet) Strombergs. There will be no market for that intake machined for newer carbs.  You probably stand a better chance of getting Offy to sell you one that doesn't have the carb flanges machined.

Art, I have a picture of one with Weber's:

Big surprise, Offy sells more 215/RV8 manifolds to England and Europe, than here.  Will "they" want Rochesters and Strombergs ?

To me Art, the only reason to run a 2x2 or even a 3x2 manifold is for the looks.
They will under perform a well done 4bbl manifold every time.
Throttle response, fuel economy and power will suffer.
But you will gain the endless joy of continuous carb and linkage adjustments accompanied by backfiring and fuel standoff.
If you must run a multi carb manifold, give the Moon eyes setup a look. They use stromberg replica carbs plumbed for fuel injection.
You get the looks, close to 4bbl performance and no fuel leaks or "gas in your hair " if you have a convertible.
They are based on the SDS fuel injection which is ridiculously easy to use.
Save the webers for a 1 barrel per cylinder application. That's what they were designed for and excel at.
If I were going to run a "multi carb look" manifold. I'd use the Offy, gut a pair of 2GC marine carbs to use as throttle bodies, hide a fuel injection spider from a GM Vortec under the manifold and run an ECU of your choice.
It wouldn't be easy, but it's simple and reliable, probably better power and throttle response than the 4bbl,  with the old timey good looks.

And that's all me and my evening scotchy scotch have to say!

Cheers
Fred

Wow Fred ,a lot of good info. !  Wish  you spotted my "OEM injection or ? " post.  Centrifugal supercharger at 8-12 psi. manifold pres.on E85. Target hp. is 50 hp. per 30 cu. in. cyl., total (6) air cooled. Fairly likely, I will make billet aluminum/nicklsil barrels, with 92 mm Mahle/VW pistons.  Thanks, art.

That's only 100hp per litre Art, totally doable.
Are you messing with a Corvair by chance?

Live like you mean it.
Fred

Fred, yes, in a 914,(Chalon).  Pretty lost on best injection for E 85 street use. Thought is to mount TB. right at the cent. blower inlet. Intercooler likely unneeded. Hyd. roller cam, reverse rotation. Info on doing this seems mystical ?  Thanks, art.