I asked about that the other day and never got much of a response, but I think the answer is yes, you can splice in a comparable gauge wire and extend them. As far as I can tell no one makes a plug and play extender harness like they do for many GM cars, etc. I'm not sure how you would go about routing the extra wire though. Does the heat shielding in the top of the tunnel area come out so the extra wire could be placed behind it rather than between it and the exhaust? If not I'm not sure if the wiring would hold up if it's mounted on the shielding directly above the hot exhaust.
BTW I was interested in this because I have an aftermarket X-pipe with HFC's which has the secondary O2 bungs much farther down the pipe--why would you want to reposition the bungs behind the secondary cats on the factory exhaust--you thinking of cutting out the primaries or something?