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

Numbers???? This is really a true story. Back about 1990 or so, I was driving out in the Missouri sticks, and I see a 70 Challenger sitting back way off the road close to a barn. (yea close). Raining. I drive over to it, no one around. It is a roller, doors locked, dana 60, boxed frame, vin on dash said 318.....HUMnnnnnnn Few days later I find the owner, he had it in HS and was second (maybe really third) owner. YEP he says, always had a 318. Knows that for fact. Yea right. I buy it and haul it home. He admitted PO buddy had changed the busted dash pad for a better one. Door deal says V code six pac. Then I check the eng/trans # on a 68 GTX I just bought from a bud that did my body/paint. Yep, the #s engine for this Challenger. It had a 4 barrel. So I unite the oem engine to the Challenger, but the dash vin says 318 of course!! Weall lived within 60 mles of each other.
Then, I meet up with a dude from Tn. that has a 66 Belvedere roller, all blasted and epoxy primed in and out. Says its a hemi car, he hauls it to my shop but it has a wedge K! and the # for the 66 426 could be hemi or wedge. We trade, I get boot. I had 3-4 V code E bodies sitting around there anyway. This is like '92. Then later I see where he has my Challenger for sale in Hemmings for some pretty big $$$$ (for that time) with the V code dash vin!!!!!!
Counterfeit dash vins back then. We ain't talking rosette rivets!!
Like the Corvette guys says # matching...so what!??