Towbar electrics

[Andir]

I'm going to be going to a yard next week to strip a towbar and electrics to fit to my 2003 e39. Can an older towing loom fit the later cars and how far must I strip the electrics out of the scrap car to fit mine. Are there any "magic" boxes I will need from the donor car.
I'm told it's a factory assembly that I'm getting.
Thanks

 

[whattingh]

there is a trailor module of sorts but to what it connects i have no idea.