This project started out when I bought a pair of GT mufflers off of Cascotech on eBay. The right side muffler is a simple bolt-on, and I figured why let the left one go to waste?
To mount the right side muffler, remove the existing muffler (unbolt 3 brackets and the pinch clamp at the exhaust) and mount the new muffler using two of the existing brackets. Save the two bolts from the 3rd bracket. I slipped the muffler over the exhaust pipe loose and bolted the brackets in place, then tightened up the pinch clamp.
The left muffler is a bit more tricky. First I used tracing paper to make a template of the right side opening. I lined the top of the paper with the bodyline on the bumper and made a small registration mark at the license plate opening. Then I cut out the paper at the existing opening (see pic 1).
Next I flipped the paper and lined it up on the left side (see pic 2). I mounted the muffler brackets and held the muffler up to make sure the opening was in the right place before cutting it.
Then using a moto tool with a router bit I carved out the opening (see pic 3). I deburred the edges with a piece of sandpaper.
I mounted the brackets, pic 4 is front and pic 5 is rear. Both pics are taken from the left side. Note that the brackets can mount different than this, but if they aren't installed like this the muffler won't fit right. Ask me how I know this
I used the bolts salvaged from the old right side bracket for the new front bracket. These bolts are not yet available from Ford, so for the rear bracket I went to Home Depot and got 8mm- 1 25 x 25mm bolts (zinc plated) and Grade B 5/16" zinc flat washers. This is a perfect match for the existing bolts. Note that the frame rails have UNTAPPED receiver holes for the muffler brackets. I suggest chasing them (screw the bolt in, then remove it) with the existing bolts before installing the new bolts. The existing bolts are easier to get aligned and started.
The brackets are Ford GT muffler brackets, part number 4R3Z-5A246-AA. I recommend getting them from KEvin at Clevenger Ford ( Clevparts@aol.com
). He'll know exactly what you're talking about, and his prices are a lot cheaper than your local Ford dealer.