I measured it before I removed my original engine since I already had a hole in the decklid for the Indy scoop. It is 2.75". The air cleaner base of a carb'd 60* V-6 using the Edelbrock manifold is the same height as the top of the 2.8L plenum.
Happiness isn't around the corner... Happiness IS the corner.
I did a measurement from the flange of the lower intake manifold to the top of the upper plenum which was 6&3/8's and the flange of the Edelbrock lower intake to the base of the cleaner flange and it measured 6&1/8" so the actual difference is negligible.
I'm bidding on a Moroso cleaner and I was double checking the height before I bought it.