[Mr70]

That block doesn't sound authentic to that Car.
June of 69 was the cutoff for the 396 #272 block.
After that,the newly anticipated 1970 model year #854 block started being installed in the few remaining 69 builds.It was now a 402 CID due to a .030 overbore,that carried the letter C in front of it's earlier two letter engine suffix code.
I too have only seen this in 402 CID.