The current issue of WIT Mag (June/July 2013) has a great write-up on retrofitting the SCS system to the newer Tri-Mark system. Has all the part #s needed, a diagram, and other good info.
One note for older coaches (yeah, my 2004) is that RVs built prior to Spring of 2004 may have an older SCS system that cannot be simply upgraded with the wiring harness.. the connectors are different.
They recommend pulling your parts list from
http://dealer.winnebagoind.com/unitsearch/parts.htm (you need your Winnie serial #) and searching for part #s of the old SCS system. Apparently if you have the #151458 or #176367 SCS systems the harness adaptor will work but if you have the #102756 system (like mine in my 2004 Vectra) the harness will not work.
They say for those older systems the new Tri-Mark System will work but must be hardwired, dealer installation recommended.