Exactly what makes a MOPAR a "Matching Numbers" car?

I have finally gotten to that point. My car might be a low production car as optioned, but I am going to cut the floor for a T56 and someone else can worry about fixing it down the road if they want. I have no plans to sell it, but I do plan to drive the hell out of it and a 6 speed makes that just so much more fun for me.
Yeah I am another one of those "bad people" who are gonna cut up "a rare car" rip out 727 put in T56. My kids can figure out what to do with it when I am gone. Original engine/trans ect ect ect will be there in storage covered in dust.....