The 250/Manual must have been a mid-year thing because all the info I have indicated it was not available until 74. Also noticed your 73 was made the same month and is the same color as mine. Of course mine is a KC car. I have a 75 Comet 4dr that was a 200/3-speed column that according to the Marti report is one of only 333 with that combo. That's only 1.3% of 4dr production. Of course earlier cars were sold with more manuals than the later ones. And the Comet is a 200, not 250. In fact it was a customer order that they must have backed out on because it sat 8 1/2 months before it sold. It's a partial stripper. They even ordered the standard blackwall tires on it. It does have AC, tint, and AM radio, but that's all. No PS, standard 4 wheel drum brakes, no exterior or interior trim items. Here's the Marti on 'em.
I may be wrong, but I understood that from the 6th month from the date of manufacture, the car was titled to the next model year. So 6 - 73 would actually be a 74 model year.
If the VIN has a 3, it's a 73 regardless of whether it sold in 73 or after the start of the 74 model year. Usually new model year builds start in early August.
3 on the tree was a pretty standard tranny back then everybody sold them the linkage always got sloppy and then they locked up between the gears didn't matter who made them ford chevy dodge linkages wore out then they were trouble