Electrical is just one of those things that takes lots of time and patience.  Fortunately the engine is not computer controlled and the amount of electrical gear is pretty small.

Here are the major components

Battery - the battery is in the trunk, so there is a big heavy cable that runs along the passenger side under the door moulding. The battery cable connects to a block in the engine compartment.

Starter - There is a starter cable that runs from the connection block to the starter, which I used the 380SL cable to hook up. There is also a cable that runs from a connector next to the block that runs to the starter solenoid.

Ground Strap - easy to forget, but the strap connects from the transmission housing to the chassis right behind the steerong box.

NSS -  neutral safety switch (see transmission for writeup)

EGR Controller

Here is the main functional diagram of the EGR controller. This was probably the trickiest part of the electrical system. I cut the pigtail off the harness in the 300D and then carefully extended the wires in the engine compartment through the firewall to the controller and spliced things in.

The black box below is the EGR controller mounted in the place of the Jetronic controller which was taken out.

Here is the color code and plug positions for the EGR wiring.  Note: I took power off the 380SL's OVP rather than bringing that unit across from the 300D.

Glow Plug System

For the glow plug system I elected to go with a manual system. It's the classic Ford solenoid system with a couple of wrinkles. I mounted a LED momentary switch in the dash under the light switch, which provides both visual and auditory confirmation that the solenoid has been activated. . 

 

The switch activates a solenoid mounted in the dash on the passengers side. 

The switch is then connected to the glow plugs. The glow plugs use the standard engine harness and connector. And by gutting the glow plug relay of all it's electronics, it functions as a fuse-holder and connector ( and looks stock). 

Finished product

Engine Shutoff

For the engine shutoff I used a manual system for simplicity and ease of use. I mounted a matching switch next to the glow plug switch and hooked it to a vacuum solenoid. When the swith is pressed, vacuum is applied to the vacuum shutoff on the injector pump. It's an extremely simple system that works really well. 

  

...more to come