I have a 91 240sx and want to swap the engine from a 96 240sx, my questions is what do i need for this swap?

This is nowhere near a reasonable swap. These powertrains differ in architecture significantly. For one thing, 1991 has OBD-I architecture, and 1996 has OBD-II. Anything is possible, yes. But some things are not worth the time and effort and problem solving. Obtain the direct replacement engine and save yourself a headache.