There are differences, & you'll need to dig through a lot of earlier threads to get the details, unless someone who knows is kind enough to post the Jonsered 670 history.
This is the tip of the iceburg:
There is a regular 670. At some point Jonsered made some changes (piston porting??) to give it more power, & named it the 670 Super.
The 670 Super won some kind of championship, & the name was changed to the 670 Champ. I don't think that there are any mechanical differences between the 670 Super & 670 Champ.
Jonsered also offered the 670 West Coast, basically a Super/Champ with a full wrap handle, some ignition changes, & a K&N filter set-up.
I can tell you that not all parts from a Champ will work on a West Coast.