67 blocks do not have a vin stamp on them, but the a-body block does have the rear mount ground down also the 2 bolts in the front need to be there, if a P/S car they are there and drilled out already - as pictured above. So for the 67 just look for a block cast 3 to 6 months before the cars scheduled production date, and grind down the left rear mount tab, if you want to be anal about it. Any 383 will work otherwise just keep it easy and find one with the two holes drilled in the front of the block for the left engine mount (pretty common) to find.
On both engines you want to verify "core shift" or lack there of to define that -search this site- there is a lot of information here on this.
