As I described on the page regarding my dual snorkel modification, in order to pull this off it is necessary to relocate the coolant overflow tank and the washer fluid reservoir. The jury is still out as to whether I am going to relocate the washer fluid reservoir or simply delete it, but the overflow tank is mandatory for obvious reasons. Here is a picture of the engine bay on a different car, showing the stock position of the tank and reservoir right where the extra snorkel would go.
On the Euro-market 107 cars such as the 5.0 special the battery is located under the hood, at the rear passenger side as seen in the photo above. This makes an ideal location for the coolant tank once the battery is relocated to the trunk.
Unfortunately, the round shape and size of the stock 107 overflow tank does not make it ideal to relocate, but there is another option from Mercedes in the form of the tank from a w126 sedan. These are everywhere at the local Pick-N-Pull for less than $20.00.
First, fabricate a support for your 126 tank to mount on the supports for the battery. I started with a cardboard template to get it sized right.
Next, I cut the pattern out of sheet metal and bent to shape, like this:
While the bracket was fairly rigid at this point, I did not want the plastic tank to be part of the structure, so I fitted a center brace underneath the position of the tank. Welded together and painted, the finished bracket looks like this:
Once together, the assembly sits in the battery position like this:
Mercedes 450slc 5.0 Rallye Project 
Nice idea! Unfortunately on my early R107 the battery is located in the engine bay.
I am moving mine to the trunk, one of the next things I am doing