If it's of any help here's my mostly-working AppleHDA kext (latest 10.6.8 one). My board is a Rev 1.0 with ALC883 (Address 2). There are no sound assertions. Tested on 10.6.8 with 64-bit kernel.
I've updated this a little. I don't think I can get any more parts working.
Green, Black and Orange analog out (good for 5.1)
Rear Mic (with ambient noise reduction)
Front panel HP
What doesn't work:
Grey analog out (AppleHDA has a limit of 4 outputs so getting 7.1 analog out means losing digital out).
Front panel Mic (enabling breaks kext)
Replace AppleHDA.kext in /System/Library/Extensions with this one.
I've now removed the Legacy kext (seemed kinda pointless when the AppleHDA kext had to be edited anyway). Its edited plist is now part of the kext.