Stock Exhaust Manifolds For 75 Duster With A 318

For a 904 casting yes I would consider those to be the same part. .......... But I do not KNOW that, and my little book only goes to 73/74.
If you do not yet have an exhaust
then there is nothing stopping you from getting better or different than 1975 manifolds. right?
If yes PM @Treblig and see what he has to offer.