I am considering buying tail lights for my 300E from a german manufacturer. Will any modifications to the wiring be neccasary?

RYAN

There are two parts to the rearlights there is the actual lens (glass) and then there is the plastic cover that holds the bulbs, complete with the wiring, against the lens. The euro and US lenses are the same but the wiring is slightly different due to the side marker lights.
So, because the wiring and the back cover is seperate from the lens you can change the lens as you see fit with anything from europe and vice-versa.

88 230E (W124)

i believe there is also a wiring harness difference due to the use of rear foglamps on euro models. For left-hand-drive cars (i believe), that should be only on the left taillight cluster.

Regardless of wether or not the wiring harness is different, the lens is the same. When you order tailights from anybody, unless you specify otherwise, you are just going to get the lens so you should have no problem.

Changing to Euro stuff up front however is not as easy

88 230E (W124)