If it is any help the route that I took from Frankfurt to Cherbourg was as follows
Frankfurt (North of Stuttgart)
Limburg
Koblenz
......
I drove to Koblenz from the UK in a 131 in 1981. It was in my 1600 Special (series 1). It was during that trip that the car developed a strange handling phenomenon. I could drive up to high speeds of 90mph or even more without any problems but when the car was allowed to reduce speed without applying the brakes, at about 85mph there was a rather alarming sideways swaying at the rear of the car which lasted until the speed dropped below 80mph. Slight application of the brakes would steady the car. The problem turned out to be due to worn bushes on the rear axle trailing arms which allowed some rear wheel steering.
The 131 and yours truly outside Koblenz. Is that map of the area still there? That?s when I also found out that the single piece trailing arm bushes for the 131 were not available from Fiat as a spare part, the complete trailing arm had to be replaced. But Fiat 124 trailing arms had two-piece bushes which were available and fitted the 131 trailing arms perfectly! In fact I still have a bag full of 124 trailing arm bushes which I can use on the 131 when I next need to?..
The 131 and the slightly seasick passengers at our destination in Koblenz