Whenever you post something on a forum, you run the risk of having a crotchety old fart like me tell you "Hey, don't do dat!!" Well, here ya go.
I did this very thing about 40 years ago and regretted it from day two, the first time a pipe joint separated in the school parking lot.
I swore off backyard designing exhaust systems then. Look at what Mr. Prior Owner did to you.
The cheapest alternative is one you only have to do once.
There are many reasons why almost nobody uses glasspacks. Whatever a glasspack is going to cost you, it will cost you that again sometime next year, if that long. It will sound like crap behind the catalytic converters. That deep rich sound glasspacks are known for doesn't happen on cat'ed cars and anyway, it goes away in about a month. So whatever it sounds like on day one will get worse in a hurry. The glass fibers get clogged with soot and harden, at least what fiber doesn't blow away out the tailpipe. So you start off with Buddabuddabuddabuddabudda and finish up with blattablattablattablattablatta.... Glasspacks are pretty hard to find in a parts store because they are not street legal in most states that don't have tumble weeds or 'coon dogs.
Glasspacks do not have baffles. They are open straight through, the same diameter as your pipe. The portion of the glasspack that is bigger than your pipe is filled with some sort of fiberous material to deaden the high pitched sounds and held in place with a tube of expanded metal. Back in the day I suppose they were filled with fiberglass, but it is probably heavy guage metal wool now, or maybe hemp fibers.
You can usually buy the clamps required to hold a muffler to your pipes from wherever you get the muffler. Make sure you tell them you want a direct fit, not a weld in muffler. I personally like steel band clamps.
I suggest a flowmaster series 40 muffler. Even the plain aluminized steel will last at least 4 years. They can be purchased individually without any accessories or "System" with it and they probably can be purchased with hanger rods in the stock locations, although it sounds like you will have to go to Ford for some stock rubber isolators. Flowmaster can tell you which one will fit your car on their website search engine, or call them. For a car that old you may need to know your pipe diameter beforehand.
Hopefully, mr. prior owner didn't butcher the stock pipes all up. If he did, you may have to buy a new over axle pipe and/or tail pipe to fill in the missing pipe. You will need the expanded or shrunken socket ends on the stock pipes to avoid doing the piece'o'pipe-clamp-piece'o'pipe-clamp jigsaw puzzle routine. And, you will need good joints to pass inspection if your state has that sort of thing.
Cherry Bomb might be something to consider too. At least they sell 'em that look like glasspacks.
To measure your pipe diameter, don't use a tape measure unless you can get to an open end of pipe and even then the end sockets will give you a false reading by at least 1/8". Just holding the tape up beside the pipe and sighting in the diameter isn't good enough.
Find something to use as a caliper (the measuring devise) and fit it around a straight run section of the pipe going into the muffler. Then measure the distance between the ends of your caliper device. It'll be probably 2" or 2 1/4" on the 2.3 liter.
I have an old rusty set of large channel lock pliers that are so crusty they will stay where I spread them. I have measured exhaust pipe by closing the handle ends up on the pipe, then measuring the distance between the points that contacted the pipe.
1993 Mustang 2.3 Talkin about Mufflers(glasspacks) 
