GMH had some stupid identication manners in the early days.
I think you need this bible:
Hopefully it will take you backwards from an engine number etc.
I can still remember mine, 448/502, build no 2905, engine number VC551104.
I think if your engine and chassis matches within the bible, that should be enough.
Your engine number is ***** correct for a Group A, should start with VC, like mine.
Getting the plates will be near impossible though.
The worst part is knowing somebody else is trying identity theft.