You will need to make sure that ALL of your safety items are fully up to snuff, especially tires and the like.

The reason that sections of the autobahn are successfully able to be left without speed limiting is because their restrictions are SO tight, that a vehicle break-down is far less common. A tire blowout that would be a daily occurrence over here, could cause a deadly multi vehicle crash over there.

However, being that your car was built in Germany to begin with, I don't think you'll need to change much hardware on the car, just make sure it is all up to spec.