Ok....I have a similar question. I also have a Sora RD330 GS on my upgrade Jamis Coda That I converted to Drops and changed the drive train to a more true road bike. I put Ultegra 8 spd Bar ends on it and they work perfect with the Sora. I would like to upgrade to a 105 qulaity on the rear derailleur. I have a spare 105 5500 GS and was wondering if it is comaptable with my cassette, chain, and shifters. I would love to put this FREE derailleur on if possible without losing the index capability of my rear shifter. Any Suggestions