Engine Wiring Harness

I am restoring my 85' 635CSi and I have run in to another wall, but this time I don't know where to look. The issue is that the engine wiring harness has lasted for many years, but it is time to replace it. It is to the point where something is grounded out and it draining the battery. Most of the plastic plugs on the harness are falling apart and the wires are cracking. Does anyone know who sells wiring harnesses for these cars?

Take it off and redo everything, replace if needed