I'm running 18x7.5 +35mm offset with 235/40 tires. From the looks of things, I'd say you could
maybe go to a +25mm to get the wide trak look. Consider that a RWD wheel is around 0mm stock to a negative offset for deep dish. A potential problem though may be caliper clearance, too.
If you really want the dished rim look, check
http://store1.yimg.com/I/speedandstyle_1743_289480 and
http://www.streetstyler.com/ArospeedChaosWheels.htm I believe this wheel has a 360-degree machined lip
behind the spokes!