Converts roughly to 30.5"x10.5".
Stock rims on an SV are 16"x6", so you'd be pushing your luck I'd say. Better to look at maybe some GV or XL7 alloys which are 16x7. Just figure out if the offset will work for you.
As for economy... they'll kill it. No two ways really about it. Jumping 15%-ish in diameter is a lot of extra leverage for the motor to push around. The auto may help absorb some of that, but expect your range to drop dramatically from stock.
www.auszookers.com/forum/viewtopic.php?f=5&t=41756