Not a 100% on this now , but it might be workable .
If you Offline the media ( move the captured clips to another folder) then FC should look to chase down the clips and I think you can then recapture them ( error comes "up media offline, would you like to recapture or browse " Kinda thing ) . As long as you logged the tapes correctly originally it might be fine , You stick the tape in and click OK and it goes to the relevant time code)
You will still need a completely different Sequence though with the correct import settings for the HDV. As a matter of interest did you use Final cut to make the footage DV or did you use a setting on the camera to export the DV ?
It can cause awful difficulties with transitions and cuts though , because of the different frame structures between DV and HDV .
If it isn’t a ridiculous amount of footage you might be better of going from scratch