The six digit number matches the phs found on the passenger front block. Yes the 69 yt crossed my mind but the engine number thing seems to eliminate a engine swap. I thought maybe they had different timing cover things going on. As I research on py forum it seems that until recently a 69 plus cover was readily available. Well now that is over and the only one I found was at Franks pontiac parts for a $350.00 tag. He said it was common to swith over for better cooling, but vary tight supply, equalling bid $$.