Wish I could be more definintive, but...
I just switched from stock tires and rims to 14" ITP C7's with 27" MudLite XTR's (see picture in my sig). I believe the offset is different as my rig definetely has a wider stance now - about 4" in the back. Of course, it may be due to going from 12" to 14".
stellarpod