ok, the 302 came out in 68, and the H.O. is basically, a higher output 302 (started in 82 I think for the 302, 72 for the 351).
As for your vin, pull off the door tag and throw it away. Some rookie cop might arrest you for a stolen car from that VIN, even though it says not for legal purposes on the tag. The VIN on the fender apron is the one for the car, if it isnt, the one on the paperwork, take the car back.