Hello Paul. Two years ago I traced the original route, which is shown as a one-page drawing in the Vom Barock zur Pagode book by Engelen, as best as I could usinga route planner software package, from Spa all the way to northern Italy, then back to Speyer. Of course the original route went to Sofia and ended in Liege, but I did not want to go that far - the idea was to use it for a European event to coincide with the German club's celebration of the 40th anniversary of the Pagoda.
My suggestion if you want to do the whole route someday is to look up the page in the Engelen book.
Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic