Not sure I can fully help and might be talking above my knowledge level but a couple things:
– I’m 98% sure HDV is just a format that lives on miniDV tapes – i.e., whether a tape is standard DV, DVCAM, or HDV has nothing to do with the kind of tape.
– You don’t say what camera you’re trying to use. If it’s an HVX200, I’m 99.9% sure that it doesn’t play HDV-formatted tapes. You’ll need a deck that plays HDV-formatted tapes. (On the other hand, if you’ve got an HVX200 and the tape is playing in it, then you know it’s a regular DV format tape and you can adjust accordingly.)
– What is the final output for the project? You’re right that your life will probably be easier if you work at the same format, although FCP 6.0 does support multiple resolutions on the same timeline. Anyway, whatever workflow means you’re transcoding the format the fewest times is the best (imo), and the final output will drive that.