I am not sure what dash parts you need, but I have a '70 Challenger that I am parting out and it had most of the dash peices. I just paid $250 for the whole car, so I will sell you a couple plastic parts for a lot less than $500.
Sorry I can't help you with a mirror though, he is very high on that too. I saw a bunch at Carlisle for a lot less. I would keep checking ebay, or see if you can find someone going to Mopar nats that would be willing to look for parts for you.