According to Tire rack: Not sure they will fit flush.
Offset: 40mm Backspacing: 6.33" Bolt Pattern: 5-120
Rec. Tire Size:225/35-20
As far as 245/40r/20 doesn't look like that's an option.
One other thing to consider is that your speedo could possibly be off as well.
What rims are you looking for? I've purchase 6 sets from this guy http://mrwheeldeal.com/b/?gclid=CISa...FayPPAodkBwAAw
best price I've ever found.
Keep us informed on what you decide on.