As Morty stated, the year model letter (B=1966, C=1967, H=Hemi engine) and the assembly date can offer you a good clue as to the engine POSSIBLY being from a certain car, but there is no way to prove that any engine came in any specific car until VIN stampings started in 1968.

That being said, it's far easier to use the assembly date to disqualify it as a possible original to a particular car simply because in most cases early year Hemi engines were assembled VERY closely to the cars scheduled production date. An engine built a month or more before or after the SPD of the car would be highly questionable. in most cases the engines were assembled within a week of the cars assembly. .02