[Schonyenko2]

There are documented 70 L78, and LS6 chevelles including the convert you mention. All with 842 heads. Your memory is fine.
While I sincerly believe in the never say never mantra, in the case of novas, the proof lies with the person making the claim. They must prove beyond any doubt with adequate evidence, that it was "born" at the factory that way. When you're talking the holy Grail of novas, you need all the legs of proof. From the window sticker/invoice, original owner information, correct mechanical configuration. etc.
It's a big deal.