Well, since no one else has posted, I'll give this a shot. What I say will be based on a 126 chassis, but there is a good chance it will be the same, or at least the same principle. On a 126, in addition to the electrical connector that you mentioned, you have to rearrange the order of the wires within the connector. I know which wire goes where on a 126, but I bet the colors and order is probably different on the 129. If this is the case, someone else will have to help you there. Since the 129s have the same type wiper assembly, both the US and euros have the one that goes along the bottom of the light, it would seem to me that they are in fact the same system and no changes will have to be made. All bolt holes should match up, and other than the small wiring, this should be a bolt up conversion.
'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.
"A Mercedes-Benz is like a fine wine, it only gets better with age."