A previous owner may have purchased a Blank door post I'd plate, and stamped an engine number on the door post to match the title vin.
How is the number configured?
you should be able to enter a door post s/n
here This info may help the original poster of this thread as well (not to hijack)
It's best to get your ducks in a row before spending a penny on a project
always a good idea to get it titled and registered
Good Luck