I think the cruise box is in the left side knee
panel check for water leakage on it. Also check the engage switches for it. One on the clutch pedal and also through the brake switch. I think the wiring diagrams, ETMs, are on e38.org under e23 section. I think e38 16 inch wheels also work. The basket weaves from an e38 should not be expensive. Get rid of the TRXs. I expect you have the OBC I which has the separate brain box that sometimes drops dead. It should be in the left knee panel I think. Look for one in a pull apart yard. The OBC IIs are self contained but I don't think started until the 735i model.