Question for Mopar and or Muscle car guys

[twitchyfinger]

I am looking at a 70 Challenger that has a "California Replacement Identification Number. There is no fender tag or broadcast sheet.
The car is not #'s matching,dose not have the original engine in it but now has a 440. I was told by the owner that the reason the car now has the Ca rep # is that back in the day the car was used in a robbery and thus the reason for no fender tag or broadcast sheet. I am just trying to figure out if the car is a good buy at 20K? Not looking for a #'s matching collector car but a nice restomod to build on and play with. Just don't want to loose money buying something that was not worth the price paid. Any help would be appreciated.

Links: http://www.cars-on-line.com/46210.html

http://denver.craigslist.org/cto/1719122263.html

Have pic of current TAG for vin verif.