The head unit will be powered by the 7 wire plug, there was a splitter that was available in the loom that powered both from one original cable
The ribbon cable connect the 2 units together, from memory there will be either blue or black or yellow or red EB caps on the cables that correspond to the markings on the back of each unit
The Gray wire then for from the head unit to the amp, which will have is own power cable with just 2 wires and then the speaker plug with 8 wires
Both these plugs will be standard flat ford plugs