It is our honor and privilege to inform you that pretty much everything in the Fox Cougar/Thunderbird exhaust system is—drum roll please—still available new! How can that possibly be, when so many other things for these cars have been long discontinued?
The OEM manufacturer of our exhaust systems is Walker, who has since become a parent company to Dynomax (now both part of Tenneco). Therefore, an equivalent Walker replacement part is more or less what we had as stock. Now, to be fully honest, the OEM exhaust systems were steel and were not expected to last more than a few years, particularly in snowy regions. But they were fairly thick gauge steel which helped delay total rust-through as long as possible.
We've got a sister article about exhaust system upgrades here, but if you're interested in just stock or stock-appearing parts, read on.
Steel tubing should still be plentiful for these cars. However, most of the industry has moved over to aluminized or stainless steel. For purists, it's steel or nothing; however, aluminized is acceptable enough for judging and better longevity, if they're available. Stainless is usually custom bent and, truthfully, it's overkill for a stock car. Save your money.
Most of the exhaust pipes, from the converters back to the tailpipes, are easy to find via a Walker catalog. Most muffler shops can get them without too much trouble. The 1988 5.0L split dual exhaust could be a bit of a challenge but we can't think of much else that would be difficult to obtain. Pretty much all of the stock piping was ~2" (5 cm) or 1-7/8". In doing research for this article we found that most of the exhaust piping used on these cars is aluminized now, and we feel that's the perfect solution for these cars anyway.
Again, these are standard Ford-type mufflers that were used on other cars, so if they're somehow not in stock, they'll be easy to order in. The Mustang and the Mark VII are two other Fords that used the same mufflers in some cases. In fact, we'd bet that the majority of other Fox-chassis vehicles used this very same muffler. Again, these are mostly available in aluminized for long life. The mufflers were center inlet/offset outlet (2"/5 cm for both), approximately 15" (38 cm) in length. Standard Fox hangers were used, nothing fancy.
Some of our cars had one catalytic converter, some had two, some had three (two small and one large) depending on the model year and engine. Probably the toughest to find would be dual 1985 5.0L converters, which were very long and narrow and used just for that model year. However, we've not really seen too much of an issue with other converters, as far as finding them. Keep in mind that, by now, the OEM converters are usually superseded by a higher-flow converter, which has a relatively stock appearance from the outside but will allow more flow internally. These are just fine for normal, stock applications and should actually be your first choice, as they're much less prone to clogging. All converters are expensive so be prepared for that.
Probably the trickiest component to find is a stock exhaust manifold. None of our cars left the factory with any type of header, so we're talking cast-iron brutes here. We did share them with other 5.0L engines but not all (the Mustang got headers; our cars had more in common with the Town Car, Grand Marquis, and Crown Victoria, but the manifolds seem to be set up more for our exhaust systems). It appears that Dorman still makes replacement manifolds for around US $100 each.
Unless you absolutely need to reuse a clamp, please pay for new ones! They'll seal up a lot better. Our cars always used the U-shaped bolt on clamp. Exhaust hangers can still be purchased via Mustang sites (LMR, Fox Mustang Restoration, and CJ Pony Parts), as well as rubber bushings for them.