Early 68 Z28 had the 302 on the frenders then later changed to the 69 Style z/28 emblem. If it has a duct it should be the cowl plenum the feeds to the passengers side of the firewall. That set up alone will bring big $$$ if sold seperately.
If its from the Org owners family, the POP just might still be in the Owners Protection Plan booklet. If its a LOS car which being from California would be a good bet, check out the top of the Gas Tank for the broadcast sheet. Also check out the engine pad for the partial VIN and the engine code. Engine code should be MO. Also check the glove box door for the tire sticker which should show it having 15x6 wheels. Then check that against what is one the car if the org wheels are still mounted on the car. Again CRG has plenty of info on this topic.
http://www.camaros.org/diffs68.shtml