I would personally just use one muffler to get the sound I wanted. I have pacesetters with ORY, no cats, and I"m running a Flowmaster 40 and I think it sounds pretty good. It is a little loud, if I were you I would consider a quieter series Flowmaster. A lot of people don't like Flowmaster on the web, but I'm not worried about a 5hp difference, and hardly anyone in my town wants to dish out the money to run a nice muffler, let alone with headers and no cats.

 

i plan on putting a 12" bullet in front or behind my aerochamber. with my LTs, no cats, and aerochamber now at about 3K rpm - 5K rpm i get that "bwap bwap bwap" redneck sound. i hate it. i'm hoping the bullet will help it

 

i gotta 12inch bullet infront of a pair of flowmasters, exits infront of passenger side tire. nice and quiet inside yet loud as hell outside, no drone whatsoever, but i can kinda hear that glasspack sound every once in a while.
mine was a pretty tight fit with an ecsb.

 

Are you sure about those specs? I have found the intermediate pipe in both 3" and 2.5" and also I have found the Aerochamber in 14" and 22" casings. If I order either and they don't come as advertised I will return them.