Question for the A-Body guys

Greetings from another Mopar Guy. I'm looking at possibly purchasing an A-Body Mopar...either a Dart, Demon, or Duster, early 70's.

Right now I'm looking at a 1973 Dodge Dart Sport.

The ad claims the car comes with the "original 360".

I was under the impression that Dodge didn't start putting 360's into the Darts until 1974, when it replaced the 340's. That's exactly what they did with the Challengers. My 1974 Dodge Challenger Rallye has the factory 360, and that is the original engine and the first year Dodge put the 360 in the Challengers, replacing the 340.

I'm wondering if maybe this was an original 318 car, that was yanked for a 360, but I don't know...and I certainly could be off on what year the 360's started replacing the 340's in the Darts/Demon and Dusters...that's why I thought I'd hit up the A-body experts. I know a LOT more about E bodies than the A-bodies, so I was hoping the experts might be able to help me.

Thanks!!