this has been covered before.. so if you have a good search im sure you'll find the old thread some where. basically the later model head lights come to more of a point in the center of the car and are slightly narrower through the middle, the bottom edge is higher and straighter..
you can get them to fit by using a dremmel and wearing out the nose cone in the center where the later model lights come to more of a point. the bonnet dosent need modding nor dose the quarter panel. there will however be a small gap 3 to 5 mil wide along the bottom edge where its narrower.
electrically they are different but i hear you can wire them in your self using spade connectors or soldering some wires in your self. bulb wise and plug wise they are nothing alike... blinkers may be the same but the rest is different.
i havent done this my self, but remember seeing some pictures and reading about this on a thread awhile ago as im looking to upgrade to the SE head lights. ill post up here when i come to this bridge