Euro headlights have a less restricted light beam and take standard H4 bulbs instead of whole sealed beam units. Brighter depends on the bulb, but the light spreads over more of the road.
The only modification needed is to the plug, and I should have mentioned I will include a 6-pin plug and point the buyer to instructions on where the pins go. Super simple, takes about one minute and you're good to go.

__________________
1985 190D 2.2L 717.411 5-speed
1983 300D Euro OM617.950