350-400 882 heads

Hello all, The heads I'm working with are the 882's. My books say these heads where produced from 1974 to 1980, and that they where put on 350's and 400's.
My question is, are they the exact same heads? I know the 400's had the extra steam holes, where the 350's did not. I looked at my 882 head and don't think I see these steam holes. Makes me think, you can use a 400 head and put it on a 350 (if the steam holes are not in the 350 block, and the head gasket covers the holes, no harm?) But you would not be able to use the 350 head on the 400 engine. (no steam holes) Bottom line....
One of my 882's off my 350 might be toast, but a guy I know has the same head (casting number) but he says it's off a 400, thus the steam holes. Can I use it? Please give me your opinions and/or suggestions.
Thanks for any help. Gene