291 heads production question

[Ls6 Ragtop]

I'm with Rixls6 on this one. Don't think I've seen a 1970 casting quite like this. All 1970 castings I've seen have the 70 for the year, not just the 1 character 0. I've never seen 01-09 used for the first 9 days of production either on the early assembly line stuff. It would most likely be 1-9. For this head to have been dated May 7 of 70 the casting date should be E 7 70. 69 dated heads do only carry one digit for the year i.d. so K 28 9 would be Nov.28 1969. From jan of 70 on throughout production GM used 70 for the year designation.
That being said, the casting date without seeing the heads could be either the first 0 might be another character such as an 8 maybe, or most likely the heads are from 1980 or 1990.
Chris