I've now installed a Webasto Thermo Top E-B heater under the hood. It will burn gasoline and produce 4 kW of heat. I'm still missing the fuel pump for it and there is a chance that the actual heater will be replaced as well, but the mount is done now. After taking the picture I also mounted the exhaust pipe where the original exhaust was located. Still missing are also the air intake for the heater, gasoline tank, coolant (heatant?-) pipes and a tank for that as well.
In the back I've mounted the charger on top of the rear battery box. I had to figure out how to make my charger IPXXD compliant (100mm stick test), hence the box split in two at the ends of the charger. It's not pretty, but it does the job. There's a pattern emerging here. I'm cutting corners to get the car into inspection shape and not worrying about the looks as much. I'll have all the time in the world to pretty things up later when I have the car registered.