I am a little confused at your explanation and don't quite get what you are wanting to do. However, here is my interpretation.
1.You have two stereo sources, 1 stereo pair for guitar and 1 stereo pair for bass.
2. You do multiple loop records, or takes.
3. After recording you want the stereo pairs to still be grouped? Is that right.
There are a couple of ways to do this but the main one involves making sure that you have the "create clip groups" preference selected so that when you loop record all the takes get grouped together. That way when you comp or edit in one track , say the Left Guitar track it will edit the same take in the Right Guitar track. Any selection in one track will get mirrored in the other "grouped" tracks.
If I misunderstood then please correct my misunderstanding.