Sorry, probably not much help to you...
But I struck this when I got my 05 3.0 Legacy a couple of years ago. Got told there should be a clock plug but I couldn't find it.., even had the stereo out to try and find it.I replaced the satnav with a cubby setup and opted for the "clock only clock" out of an 06 on facelift model.
I tapped into the satnav plug to do this but can't remember how I did it now. My research at the time suggested that if I was to get the tripmeter part working I would need to pull out the cluster and tap into that for it to work?.. which I decided not to do..
I found the American site LegacyGT.com usefull at the time..
Cheers