swap meets in se pa
You can also find mopar stuff at the Spring Carlisle collector car event, it is normally the first weekend in April.
There is a lot of Mopar stuff on craigslist also. I live south of Washington, DC and have bought a few things off of craigslist lately (340 manifolds, air cleaners, valves, "308" 360 heads, slicks for the racecar, etc). I also bought a 4 speed set up for my cuda from a member of this board, and recently found a fender for the cuda through a "word of mouth" recommendation from another racer , so you need to beat the bushes on all fronts, but you can find what you need if you are persisitant!
Good Luck,
Bob
PS: what are you looking for??