Bizarre SB 915 Heads

Loco is correct, later 77-79 casting heads. They were common on Van's. Anything that didnt get or require air injection would not have the holes drilled.
The 25 , 2 or 3 digit. Is the month or year of casting.
I've always assumed they were a J intake core brought back from the dead combined with a 587 version exhaust port. The better exh ports were on 974/596/308 heads.
They are 348915-J heads with a 025 or 25A or something like that.
Went to those same heads in this thread when the 1st set if 308's were sunk.
Intro to a port job