what is original, what is rare option, what is not?

Hello. i picked up a 1973 swinger. The first thing that caught my eye was the police push bars, head light guards, and '70s style fog lamps. As i got closer, i noticed factory bucket seats and a tow hitch... interesting. Looking underneath- i saw huge leaf springs, and 742 axle, power disc brakes, anti sway bar, and large rear drums. When i popped the hood, there was a super six motor with all of the heavy duty additions(over-flow, 7 blade fan, shroud, trans cooler, etc). Now, my questions:

1) Why does the auto parts stores, in the US, show a "Mexican" 2v 225 slant six for 1973, when i go for parts, when a super six wasn't produced until later. Is it possible that my motor is original?

2) How rare is the tow package option?

3) Have you ever seen push bars on a Dart?

4) my swinger has rear defogger, rear defroster, remote trunk lid switch, map lights, dual side mirrors. i'm wondering, are these rare options or part of the tow package?

5) Lastly, was a 8 3/4 742 produced in 1973? for a dart?

Thanks. all help is appreciated.