[DanEC]

It's nice and cool in my house and I'm too lazy to go out and look at my engine that is sitting in the corner of the (hot) garage to verify my foggy memory but I believe the carbs are mounted backwards so that the primary barrels of the front carb are not that far off center of the engine. I can't see a lot of difference with this as compared to a low performance 2 bbl carb as far as fuel distribution to the various cylinders goes. Holley Performance may not be aware of that.

I fail to see how there is much risk of overcarburetion too. Up to about half throttle you run off half the front carb or about 300 cfm max. At more throttle opening it brings in the primaries on the rear carb up to a max of about 600 cfm. And beyond that, engine demand will bring the vacuum operated secondaries in only as vacuum demand and carb calibration require. I doubt the secondaries on the front carb can open at all until your getting into the second carb. I guess it could depend on the springs in the secondary diapragms.