Could use the main harness, just need it to have all the connectors on it (or most at least), don't care if it works or not. same story with the tail light, could use it plus as much of the mounting hardware as possible (any brackets etc). Side project of mine is to try to source some sort of aftermarket tail light option. Harness is just to complete my 185/200 collection, thought I had one but can't seem to locate it.
Sent you a PM