has any one fit edlebrock performer intake in a 73' deville. also they say you have to move the ac compressor, mts has a ac bracket for the performer, does this work with the stock pulley system. and is this a good performance upgrade does it change the mpg.

I believe the first thing you should do is call MTS about the pulley arrangement for the re-positioning of the AC pump, and while you are talking to them, ask about hood clearance. Those are likely the folks with the answers.

Some folks here believe there isn't enough room under the hood, and they are likely correct.
I guess you could mount a Z-28 hood scoop for clearance. Those are available in several places, in plastic and fiberglas.

The folks at cad500parts.com ( Flashcraft) also have the brackets for the pump. You could call them also for info.

For the guys overhauling the 472/500 engines, Flashcraft has a new stainless steel front cover plate, which is sometimes rusty as hell and full of pits etc. Mine is, and I'm gonna get the new plate. It's around $125 bucks I believe, and takes care of potential water leaks.