Died in March of what year?  If 2024, then income through date of wife's death goes on final 1040, income after that date goes on a 1041 return. Generally speaking.  Every trust is different, except for the ones that are all alike because they use the same boilerplate language from a paper mill.   

@sjrcpa If you don't like joint trusts, you're lucky you don't live in a community property state.  I don't like people who bring their separate trusts from common-law states.  Or, more often, all of the property is just in the husband's trust.