Getting started to work on my 1974 Dart Sport. I got questions

So according to the VIN it was indeed a 360 car originally, and that would get you an 8.25 rear differential with a 727 transmission. Next step is to determine what has been changed other than the engine, if in fact that is a 340, not just the air cleaner decal. Car looks to be in really solid shape which is a great starting point.