I would think your first step would be to learn more about what exactly a “California Replacement Identification Number” is and how and when they are applied to vehicles. (It sounds a lot like a "Salvage type title" which could mean this Challenger has had major damage in the past.) But be forewarned that any unusual title such as this one and the fact that the Challenger is missing its original VIN Tag means this Challenger will never be worth what an identical Challenger with its original VIN Tag intact would bring. This may or may not mean much to you right now, but…..in the future it may. The main issue is you (and any potential future buyer) will never know the true identity of the vehicle in question.
I would have the Challenger inspected by a “good” body shop to see if the car has ever been in a major accident, and whether the car has been spliced together….etc.

Having said all that, if you are looking for a “Fun” driver, and not a future collectable, and this one checks out …..It looks to be a very nice buy. Just do your homework “before” you buy. But to be honest with you, I would more than likely pass on this one. But it's really up to you.