Is a Holley 750 DP too much carb?

The OP is way too green to be tuning air bleeds and emulsion, and that's if his carb is adjustable.

Certainly he can drill and tap all that stuff and make it tuneable, but he's better off paying someone like Thumperdart on here and over at moparts to do it for him.

I'd leave the gears you have in there. A bit taller tire. And let it go. If it's not you daily driver, what's the difference between a well tuned 12-13 MPG with what you have, or 16-18 if you go to taller gears. You'll give up a butt load of performance with less gear.

BTW, higher numerically is a LOWER ratio. For example, a 4.10 is a LOWER gear than a 3.55. It is higher numerically but the ratio is lower. You are always better off specifying ratio than numeric value. Sometime in the 1990's the numeric value started getting tossed around and has become a bad habit.