First, search google for your vin. Then search other platforms as well. duckduckgo comes to mind. Research any lead that comes up.
If nothing comes up you can post wanted ads with your vin number on it.
That will get a lead to you when someone else types in your vin number.
There is of course Barry Washington. He's probably a member on here.
He owns the Hamtramck Registry
The 1970 Hamtramck Registry - Challenger T/A Registry Home Page
He does not share information. As I have asked numerous times for info on M46 cars. No luck, even though he's said he has info on build sheets but will not share the info. So, all you can do is send an email or call and ask if your build sheet happens to be in his registry. If he has it he will gladly give it to you with proof of ownership (as I am told).
Delve into his website and you will find where he has listed many bits of information that are "found". You might get lucky.