81bird

So i was lookin at the heads on my 302 i bought from a guy. The identification i find is on the top left it has 15 and right has a S, on both heads. Can anyone tell me what heads these are, I searched the heads all around can find any other numbers/letters. The guy i got it from dont remeber what was done to the motor. I already got GT-40P's to put on it but im just curious to know what these are. BTW. The motor is 88h.o. out of a mustang gt. Thanks alot rob.