I would like to know if there is an existing hole in the E36 body through which a Trailer Tow Hitch Wiring can be routed or do I have to drill a new one. Also, is there an existing electical plug in the boot somewhere that can be used for connection purposes?
As far as existing holes there are lots in the boot, they are covered with black rubber plugs and can popped out replaced with a grommet or just cut a hole in the middle to run cables out. I don't believe there an existing plug for you to use but the Bentley E36 service manual would be your bust bet for finding out/finding the best place to tap in.