Swap front derailleur clamp?
I am trying to move from a double to a triple as well as moving from downtube shifters to STI and am having some issues with the front derailleur. I currently have a Shimano 105 double front derailleur from circa 1992, but it is not shifting to big ring at all. So I am shopping for a cheap triple front and am not finding one with a 34.9 clamp that I currently have. The questions I have are:
1. Can I buy one with a 28.6 or 31.8mm clamp and swap with the clamp I currently have? The clamp I have is attached to my front derailleur with just a allen key bolt.
2. Are Sora, 105 and Ultegra front derailleurs compatible?
3. Are there any differences between 8, 9 and 10 speed front derailleurs?