I do this regularly and like to keep the scratch audio but you can still have the external track to cut with and get rid of the others in the timeline (or solo the tracks on the master clips).
Sync everything, then group. Set up the Source monitor so that it displays multi-cam angles and so that you have the option on the top gray bar area (like where you choose to Load Filler) to display another track of info. This way you can check off the audio tracks you want and video and audio follows video and all that. I’m not sure what you call doing this, but sometimes Avid defaults to showing less info up there, and you need to see more info about your grouped clips.
So then you should be able to choose your audio tracks. Then cut into timeline whatever you want. If it’s the wrong audio, right click on the track then choose the other track.
Hope this is what you need…