I doubt it. Usually the harnesses are for Hyundai and similar. Unless you are 'good' its a trip to a radio installer. BTW the three worst people to follow into a dash are 1) Radio installers 2) Alarm and Imobiliser installers and 3) Plumbers. Hope you know a good one.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i