[Three Peaks]

First off, the Edelbrock Air Gap is a dual plane manifold so your low end should be fine once you have the right carb and tune it correctly.
Which 750 are you running on your engine? What cam are you running? Have you had it dyno tuned and jetted properly for your set up?

I've heard from lots of guys that the 750 is great for the 393 at the top end, but loses the bottom end power. Just the opposite with the 650 DP or 670 Street avenger- great low end, but not enough top end.
I think a bit of tuning with your present set up will probably work wonders and give you the engine you thought you had.

For clearance on my 393 I got a dropped base 14" x 2" air cleaner . You can get the dropped base air cleaners lots of places. I found mine cheap on ebay, then bought a custom top to add a little bling to the engine compartment.

Bob