For visual reference:

Original 1995 Skandic WT Chassis:



Yeti Chassis:



Yeti Chassis in SUV Trim:



Yeti II Chassis w/Strut Front End:



Yeti II Chassis w/SUV front/rear end, also known as the TUV platform:



The latest Utility WT platform, the REV-XU, introduced in 2009:



The Rev-XU Chassis w/struts, introduced on the 2010 Tundra/Sport/LT:


(With any luck, this chassis will replace the Yeti II w/struts!)

Some general notes:
- The Skandic SWT switched to the Yeti II chassis in 2007.
- The Skandic SUV switched over to the Yeti II chassis in 2008 if I recall correctly.
- Not 100% sure, but I believe that the Skandic 600WT in the Yeti chassis was phased out of the line up in 2003 or so when the SUV and Expedition started taking over, but has made a re-appearance in the Yeti II platform in 2007 or 2008 and is a great addition to the lineup.