yes they do make a muffler that will fit the ZJ's. you just have to go and get a "generic" fit muffler. the shop where you are getting it from should have an application guide for your jeep. you just have to get the right ID and offsets for yours and it bolts in.
i did need to get a 12" extension pipe to get it to fit, but it was no big deal.
The Almighty 2" BB Jeep Club Member #34 (no more BB)
[B]Silver 98 ZJ 4.0 I-6[/B]
K&N FIPK Gen II
JKS Adjustable Track Bars F and R
JKS Adjustable Control Arms
JKS Quicker Disco's
Kevins 3.5" Lift Kit w/ MX-6 Shocks
US Wheel 15x8 10 spoke black Steelies, 31" BFG AT KO rubber
i have a flowmaster 40 series for my 93' 5.2 and it sounds really good. the flowmaster is going to be a little smaller than your factory muffler so they will put in a little piece of straight pipe. i got the muffler replaces and kept my stock pipe and it was $115 installed. it will sound great.
I have welded a number of flowmaster 40's on for all my buddys with I6's and they do sound great, just call some muffler shops around town and see which places carry flowmasters. You do not need a bolt on kit or any of that junk. If you want to open your exhaust up even more i would suggest a highflow carsound car or even some heddman headers for around $115. I6 are great engines for exhaust and they do not sound like crap in any way. All jeep engines have a very disinct sound and they all sound great with flowmasters. Just dont go the cheap route and get glass packs or any other kind of muffler for under $50 because you get what you pay for and thats crap
1994 Grand Cherokee Ltd V8, Rustys 4.5 lift, Daystar 2" Spacers up front, Rustys Intake, Rustys Adjustable LCA's, 31x10.5 BFG MT's, AR 767's, 3" Carsound Cat, 3" Pipe, Flowmaster 50 Series, Mike Leach Headers, Clear corners, Billet grille, 5% tint, Front and rear Trailready Bumpers, Cowl hood www.cardomain.com/id/xxhotelcrazyxx
mandrel bent (pre made catbacks) have a better flow rate because when you have a muffler shop do it they simply use a pipe bender and therefor can have somewhat sharp bends, but it really isnt to much of a problem if you have an experianced person working with you, i just went down to my local shop and had them slap on a 50 series and bend me up some 2.5" piping, it sounds great and was only 140 for muffler+pipe
[SIZE=1]91 XJ Laredo
6.5" Rustys, RR Adj Trac Bar, RE Adj UCAs/LCAs, DT3000, M.O.R.E steering box brace, Rancho steering stabalizer, custom cone intake, Poweraid TB spacer, home-brew roof rack, lights everywhere, +10 HP Jeep Seatbelt pads, hole in the fender from previous snorkel, plus a lot more crap