I have the exact set up on my 88 gt, they fit perfect, the lx tails are shaped differently than the gt pipes so they "hug" the gas tank more, no problems with mine at all. They get alot of looks too. good luck
Did you use a complete kit.. if so which one. I am currently using 2.5" flowmasters and flow tubes with dumps that were once part of a gt cat back. the tail pipes I have are dyno max i believe, and they don't match up with the mufflers very well at all. seems like the mufflers need to be moved toward the front of the car an inch or so. Plus the hangers are too short which isn't a big deal. It might be easier to sell what I have and just buy a kit.
I bought mine from www.texasmustangs.com and had the same problem, i work at a shop so i was able to use a torch and pipe cutter, i have the same set-up that u have. it was a flowmaster 2 chamber for a 88 gt then i ditched the gt bumper and bought a cobra bumper, then bought the lx tails, I cut about 3 inches off the drivers side pipe to make it fit, only about an inch or so on the pass side. the biggest pain was having to move the muffler towards the front of the car. I had to cut at the flange, about 2 inches back, the re-flange it. it was a bitch of a time, i thought mayeb the tails were supposed to be for a newer model or something. they look great now. as for the hangers out back, just take a pry bar and give em a few pulls, they go wherever u want them to. I'll try and post a pick for you.
Thanks.. I'm sure the muffler shop is going to like this project.. And I'm sure I'm going to hate the bill for it. They wanted 50 bucks to just cut the turn downs off, weld the pipes to the mufflers, and extend the hangers. So I'm sure when they figure out they need to shorten the flowtubes the price will go up