I looked at Wallace Racing and the casting # for 1969 GP XH 400 was listed there as 7029268.
I did some more research and found this site;
https://wowmusclecars.com/pontiac-engine-codes-specs/
There I found "1969 400 XH 9790071 4 Bar Carb 350HP Grand Prix" . just what is stamped on my blpck.
I can't tell what was ground off, but a 4 bolt main 400 that came in a 1969 Grand Prix . OK