IIRC, the 3rd gens have a better/longevity transmission.
The '94 fuel injectors have a different impedance than the '88's, not sure about the other electronic components. If it were me, I would pick one year and stick with it for the efi components, and sell the other system for a conversion, if not the entire engine.
The '94's seats will fit in the '84, may have to use a small spacer(1/8-1/4") under the outer rear mounts to level out teh back of the seats.
