Steve the 915 casting number is used for the 1970 TA head and non TA heads made from 70-72 (don't ask me why Ma Mopar used the same # for different heads) but the TA heads are different because they have offset intake pushrods to allow more intake port opening. The other 915 heads are the same casting design as any other small block LA head. I noticed yours have the offset pushrods and rockers which makes them the TA heads.
Your a lucky man. The TA heads are worth a small fortune.