Nice Challenger w the 340 and 4 speed.
I noticed it had been signed by Richard Petty.
Have you tried contacting the Mecum Auction House? They may be able to help you.
Good luck with the search!
You should be able to put the VIN out there and the DMV's can tell you what state it is in and start narrowing it down that way...even if you have to call the DMV in each state?