Need help pulling my 273

The motor is out and what I have learned is that the small block LA engines just barely fit in those early a-bodies. I'm sure there was an easier way but we had to pull off the exhaust manifold while the motor was slightly elevated to get to the top bolt on the starter. Once that was done we where able to separate the engine from the trans. After that the motor came out pretty easy.

That was last night, Fast forward to today I kicked out a few of the freeze plugs and it look pretty rusty inside I guess that is to be expected. Now I have a few questions First how can I confirm that my car is #'s matching? Second I'm half temped to put in a /6 and keep the 273 out to rebuild. Will a /6 line up with my 3 speed auto trans. and if it does what will I have to do to make the change? Third question can I pull a power searing unit out of a 72 dart and drop it in my 66 cuda?

Last but not least I would like to thank my Friends 74DartCustom and Ptdartfreak for coming over and helping out! :-D