Factory Dart Chargers were only manufactured at the LA plant and the order number starts with 70xxx. Kit cars from LA, St Louis and Detroit order numbers starts with 06xxx but the Vin starts with L452(Detroit), L455(Los Angeles) and L457 (St Louis).
All factory 273 4 barrel cars had a special cut our on the left side on the rear valence.
Re the production figures for 1965 Darts with 273x4 was 7560 cars. Of those cars 4157 was automatic, 3247 were 4-speeds and 156 cars were 3-speed on the column.
If a Dart was equipped with a 273x4 it has 31 stamped under AB in the middle row of the fender tag.