I'm inclined to agree 100% with Lynn on that. While having no tag at all may prompt more questions, the answer is always easy and the same. If there's a repro tag on it, it won't get the obvious question as before, but before too long there will not only be more serious questions raised, but a lot of talk about the car and it's "real" heritage that you will never hear. Afterall, what body number would you put on it? You'd have to make one up, and it sure would be a shame if a car with it's original tag showed up with the same number. That could cause problems for 2 people, one of whom doesn't deserve any controversary over his car....
I also have to wonder about something else. No harm intended, but you stated the original cowl tag was destroyed in an engine compartment fire. Now, I have to think about how severe that fire had to be to completely melt away and "destroy" that tag. You also state, "The car is all original, paint, interior, engine, tranny, rear"
I have to wonder what might happen to the paint on a car's fenders, hood and upper cowl in such a fire......

Was the windshield cracked from the heat? Was the firewall pad toasted? Paint has a lower melting point than aluminum.
I said, I'm not trying to start trouble, but from what I've read so far, in my opinion things are sounding a little fishy.......