Where can I get a down pipe for my 85 wagon?
Walker used to make these, but stopped quite a while back. Maybe an old-timer parts house still has one hanging about somewhere - probably out of luck tho. Try Waldron's Exhaust. They may be able to make one for you. I've used them in the past for other AMC applications. Call them, as their online catalog is not a complete list of what they have bend cards for.
If you go to a real muffler shop, they'll be able to make one for you. The Walker ones are tough to come by, when I needed to replace the cat back portion of the exhaust on my Kammback, they had to custom make it at the shop.