In the picture it looks like a secondary metering block would fit on that front carb but it actually doesn't. I tried it and you would have to use a press fit to get the carbs to fit.

But, there is non particular reason why Indy couldn't spread the carbs apart by another 1/8 or 1/4 of an inch. These manifold tops are machined on a CNC vertical mill and there isn't any magic to the exact carb placement. So if a person wanted it done that way I'm sure you could work with the guys at Indy to get the carbs moved apart.