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

I ordered a new 70 Duster slant car Dec. 26 1969. Lucky me, when it arrived it had a 426 hemi....the dealer said they ran out of stants that day and there it was with my hemi!!!!!! True story! :steering:
Stop by so we can go for a rip, I definitely want a burn in that car :D:D:D