newbie from idaho needs help!

I posted this on the welcome wagon but it was suggested that i repost it here. I am in the middle of restoring a 70 belvedere with a 318.the motor was badly cracked from freezing,so I picked up a 318 from a wrecking yard out of a 69 pickup.I didnt notice till I got the motor home and cleaned up that it was a 1974 318. I think I am ok with it though. the problem is that I am trying to identify the heads that are on the motor. the casting # is 3870277 on one head the other has a -1 after the #. It also has cast into it 0425 aawj. and also has the word TRUCK cast into an intake port on each head:banghead:. I have been to just about every site that has head casting #s but the higest # I have found starts with a 376. I really need to identify these heads before I decide what to do with this motor. any help at all would be greatly appreciated. thanks for the welcome and I glad to be here.