You'd probably be better off posting in the ICE lounge matey.
It is hard if not impossible to give you a definative answer mate especially not knowing what plugs you're looking at.
The only thing I know and it may, or may not, be of use to you is that the GPS / Connect Nav system uses the same plug setup as the standard unit, being the double 2 x 8pin plugs and the the yellow / green / blue mini ISO plugs.
The 2 x 8 pin plugs, top one of the two should be the speaker line outs and the lower one of the two is the power supplies and switching.
The mini ISO plugs yellow should be line outs, green should be remote controls and blue for CD changer.
The Connect Nav has 3 other plugs, one is green, another is grey which I believe are only 1 or 2 wires - i think this are GPS and GSM arial connectors, although I could be wrong. There is also a bigger white plugs although I've no idea what this is.
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso