Stock parts, resources, suppilers....

Hey all, I'm a newbie here on FABO. I look forward to learning from others, experiences, and hopefully paying it forward to the next guy some day. I am the proud owner of my first "real" mopar. (I just cant count the Chrysler minivans)
A 1971 Dodge Dart Coupe. 225 Slant 6, Rust color paint?? Registered her as an antique. A work in progress for sure but hopefully a sweet solid driver in the future. My question: where is a guy gonna find parts, ie, a stock exhaust for a slant 6 dart? Seems like Rock Auto suddenly stopped carrying parts they used to have just a year ago! Like most I'm on a budget so please dont send me to Year One unless they are the ONLY alternative available. Any thoughts gents?
Post a pic? Sounds like we have the same car. Have fun.