[Mark Yacavone]

I never noticed the spec difference but I think i know what you're talking about.
I saw some tech guys looking at a brand new Edelbrock one time.
It looked like the factory had taken a bearing scraper and removed the casting seam in the venturi.
They must have given the E-brock a little leeway.
I doubt you would get away with the same thing done to an OEM GM bowl.