Stumbled across a Campagnolo Gran Turismo Rear derailleur, anyone know anything about these? all I could turn up was they were inexpensively made and did not shift as well as Shimano Crane. How do they size up to more modern derailleurs, or older derailleurs?
Thanks

You pretty much provided a good analysis on your own. It is not going to touch a modern derailleur and the old Suntours shifted better for the most part. But if you want it for nostalgia or that final piece of the puzzle, go for it.

I've never had any problems with my Gran Turismo. Maybe they have a unjustified repetation or that I just shift carefully.

My '71 P15 Paramount tourer came with one. It did the job, but not very well. I replaced it with a Rally which shifts much better. Some say the Rally isn't all that good either compared to a SunTour VGT-Luxe or a Shimano Crane GS. I agree with with CV-6 on this one. If you need one because it is the correct part for your restoration, go for it. Otherwise, the SunTour or Shimano are generally cheaper and far better. You probably know this already, but the Gran Turismo is a wide range derailleur for touring which is why I mentioned the VGT-Luxe and the Crane GS. If you don't need the wide range, don't bother with a touring derailleur. The short cage derailleurs will usually perform better than the long cage ones.

The Gran Turismo does indeed get a bum rap. It was designed to be used on bikes with only one single chainring and a wide range freewheel. Contrary to most Japanese competitors, it is virtually indestructible and will rarely if ever need to be adjusted, a feature that fits in well with the target market for the derailleur. The Japanese derailleurs shift much better but are notoriously fragile and prone to need adjustment. The Campagnolo works well on those bikes sold to the large majority of weekend cyclists who do no maintenance to their bikes and have no technical understanding whatosever. In its day, it was not at all bad for its intended use. It does not however belong on any 'serious' bike.