Iding a Pontiac motor

[ClassicCar.com]

Hi,I need a little help Iding a Pontiac motor. It is in a 69 Firebird. It is a v-8 with YN stamped on the block.I cant find this in my books for 1969.Any help would be greatly appriciated.

[ClassicCar.com]

Annon. you have a 350 2bbl engine 265HP gross.(I believe about 160HP net.)

[ClassicCar.com]

Ron thanks, would you have any idea what year it could be or what it might have come out of from your sources.