The OP'S bike is a beautiful example of the bike boom era. All European components. And it's stayed unmolested for 45 years. When I see great examples of bikes from this era my philosophy is to preserve their heritage. Keep them period correct or upgrade them with components that would be fitting. Sure Suntour derailleurs were a popular choice back in the early 70's, but a Simplex LJ or Campy NR would carry on the European flair this bike possesses.

That's my philosophy and I am sticking to it.

As far as the influx of Japanese components on European bikes in the late 70's goes, I find that time in cycling the decline of the European bike. The Motobecane Grand Record for instance. At one time it sported TA cranks, Campy derailleurs, Normandy Luxe Comp hubs, Atom pedals - a tour de force of euro components. By the early 80's it was outfitted with Shimano 600. It just seemed lackluster in comparison to what it started out as. At this time a lot of bikes seemed generic as Japanese components proliferated.

Just my opinion. I rarely buy bikes post 1974. So I am very biased in my views. But we all have our own "thing" when buying and refurbing our classic machines.