I have the American Thunder FlowMaster system on my 5th Gen (1980) with the G-Force Crossmember. Borla makes a better set of mufflers but I stuk with the packaged deal. I purchased mine from Jeg's and I also got some Hi-flow cats, just because. The American Thunder comes with the pipes, hangesr, mufflers, and two sets of tips. It exits straight back under the bumper not behind the tires or in front. The one I got was 2.5" Aluminized pipes. I think they make a 3" kit, but could be wrong.
According to the discription in Jegs the system comes with two tailpipes--straight out under the bumper or trned down before the bumper. Personally I prefer exhaust tips just behind the rear tires and I guess you could modify the system?
The one I put on the 76 was about 2 to 3" too short, not a problem I put chrome Tips on it anyway. The One on the 80 was about an inch or so too long with the tips provided but I installed some Edelbrock Resonator tips on it so I didn't have to cut that either. But if I just used their tips then yes you'll have to cut the tips down. Its not a big deal. Cut the end that goes into the pipes and you never notice. They suggest that you have the pipes welded once you get the adjustments done, I didn't. The system is "H" type connection just after the header connections. So if you do not like the "H" type of set up then I wouldn't suggest that you go with Flowmaster, I suppose you could cut that out if you wanted..
DynoMax makes a Dual Exhaust set up that comes out behind the back wheels I don't know anyone that has used those but DynoMax is a good brand name so its probably pretty good. I don't know that they come with Mufflers. Also G-Force makes a "Cat Back" dual exhaust specifically for "G-Bodies" but its dual after the factory Cat. It comes both "SS" style (straight out the back) or behind the tires, your choice.
I have the dynomax system on my elky. they make a 2 1/4 dual exhaust kit for fifth gen malibou or monte carlos that fit from headers back. it fits with the stock cross member with no mods of any kind but for the elky you will have to add a extra foot of pipe on each side to make it long enought. it comes with hangers and every thing to install and for a real good price. i think summit sells them in the US. it comes out below the tail lights, but mine didn't come with the mufflers to see a pic of my system its on page 8 of members cars.
Hi Tommy the left front pipe is bent around under the factory cross member and its a perfect bend and it looks like it should of came that way from gm. and i never even lost very much ground clearance and i never ever had my pipe scrape any where and our roads are in pretty bad condition. the first nice day ill try to get some pics of the left front pipe and post them. the system was a bargain at about half the price of the muffler shops around here.