Whats the easiest way to find "302" heads?

The othe day me and a couple friends went to a auto wrecker to find a pair of "302" heads, but this auto wrecker they take the parts off for you. See im new to all this so i cant really tell the differences between engines, how can you tell if its a 360 or a 318? cuz we found a truck that was the yr 1988 but we donno if it 318 lol. Where can you find the casting numbers to tell that they are "302" heads? just thought i should get some info on them be for i go get one of the guys at the wrecking yard to go take the heads off then find out there not the right ones.

Thnx, Adam