In '68 ALL performance engines (P, H, L & J) & their associated transmissions were stamped with the last 8 of the VIN# (340 383 4bbl 440HP & HEMI). As these saw the majority of warranty claims due to their intended purposes. Lesser drivetrains were NOT stamped.

The S.O.# can be matched to an appropriate VIN# if one has a large enough database to access, I have a pretty good '68 Charger database - GG & a number of others do also.

If it gets to the point of a legal issue, the authorities have records to match the correct body numbers with the correct VIN#: subpoena 'n lawyers 'n $$$s etc.