Hey David,
I don’t think you want to “overwrite” your material – it sounds like you just have to get some organization out of the way and then batch capture your material.
1) Scroll over to your Reel column in the browser – when you captured the original material before rearranging projects did you keep the titles on your tapes and fill out the Reel name in the capture window when you were capturing so you know what clips are associated with what tape?
2) If you did, great just select the clips in your bin that associate with each specific tape and batch capture for that tape/reel. If not, you can manually change the Reel column according to what tape you think the clip is associated with, and then do batch capture for each tape.
You should be able to get away without having duplicate footage if you implement this correctly. Hope that helps.
– Evan