There are many variables to take into account such as
January 26 2002, 7:25 AM
which year and block...passenger car C6ME, mirror image 105 block, heavy duty 391FT block, etc...but there seems to be no real 100% fool proof method with out sonic checking the block. We had a C6me passenger car 390 block that would have only of had .095 wall left on the thrust side of a cylinder wall after a .030 bore because of bad core shift and this is a standard bore block. I currently am running a .080 over 105 block which comes out to 406cid. There are several past posts to this general question on over bore.
427 the code he shows that is on the timing cover traces back to a 427 block but there could be a totally diferent number on the block than the one on the timing cover. Anyway. Oh one more question what would you all say a motor like this is worth with tranny?
and figure he meant to write 428 but due to a brain fart put in 390. But since I am not going to bid on it it doesn't matter. I would at least contact him first to see if that's what happened. My 2 cents anyway.