Usually a 1968 VIN third digit tells if the car has a L6 or V8 (3=L6 4=V8) but is it always like this? I have found a car that down to details is a SS 350 but have a VIN starting 123. Also looked at this video on another 1968 that seems to have same issue, but with 327 badges https://youtu.be/_cA_TNPNve0?si=u21tMDdi3MJXMlyU
On a 1968, if the VIN tag, on the dash under the windshield, starts with 123 then it was a factory 6 cylinder car.