Forgive me if this has been brought up before, but Walker Exhaust no longer lists the V6 muffler, part number 40094, which was what I purchased for my 86 GT probably 4 years ago through summit racing.
That does suck, but to be honest, I replaced the stock muffler on my 87 GT with a Walker about 2 years ago, and have never been happy with it. The stock muffler (cat delete) sounded SO good......it just purred, and sounded great at WOT.
The Walker replacement......too tame IMHO. I'm considering changing it out for something else, it just hasn't been a high priority for me. Though I really miss how great my car USED to sound.