This car has dual exhausts, and does not have the cut out rear valance that I have seen with other 273s. -- Is it possible that this is one of 271, or just a copy ?
do you have a build sheet to corroborate the information?
none of the early cars came with duals from the factory, and there's no cut out on the valence so that may be your first set of clues. however, a lot can change in 60 years...