According to the iSync Device List, the Motorola C350 is supported by iSync. But my phone was not found.
There are small differences between the supported model and mine. Using USB Prober my device announces itself as:
Device VendorID/ProductID: 0x22B8/0x5802 (Motorola PCS)
whereas iSync expects a ProductID of
0x3802 for the C350.
Copy the MotorolaC350a.phoneplugin folder into one of these folders:
- /Library/PhonePlugins (makes the plugin available for all users)
Then plug the phone with the data cable, restart iSync and Add Device… and the phone should be found immediately.
There are now at least two sites providing iSync Phone Plugins (which I haven’t tested):
- Steffen Zimmermanns DIY iSync Phone Plugin, featuring my “Script” (the Property List file) for the Motorola C350.
- Nova Media has a Free iSync Plugins page.
 This file has a rather long path: