the engine loom unplugs from main loom. the only wiring you need is
green - from coil negative to rev counter
red - from permanent +12V to both relays (pin 30)
black - from switched +12V to both relays (pin 86)
black/red - from fuel pump relay (pin 87) to fuel pump
brown/white - from temp sender to temp gauge
These are the car-engine loom connection