I have a supper 44 (flowmaster) on mine. I used 2.5" and just used adjusters from O'rielys to fit onto the stock 2.25" tubing.
Notice the video's jeep does not have exhaust tubing after the exhaust going to the rear of the jeep into a tail pipe be the rear right tire, that would be fine but I found on Our 4.0s the pipe after the muffler helps with sound (IMO, plus having exhaust under your jeep is never a great idea). I had a leak coming from after the muffler where it connects to the tail pipe. it sounded bad like a cavalier with a rusted out exhaust. (3.9) but after fixing all leaks it sounds great.
Id post a video but Can't/ dont know how. I personally like it.
But REMEMBER, it will always be a 6 cylinder