With the offset you mentioned, even a 6.5" wide rim might have enough room behind it for a wheel adaptor. Adaptors don't have to be very thick to "hide" the fasteners. 740 rims, with a bit more positive offset--I think 30mm (offset toward the center of the car) than 240 rims, fit the 240s, but they really sit too far in on the rear. Spacers and longer studs get the tire closer to the fender lip and make the whole setup look better. I think you should borrow a rim, put it on the car, and then experiment with a stack of washers to see how far out you can move the rim and still get clearance at the fender lip. Check at the front for clearance to the strut spring perch too. If you've got 5/8 to 3/4 to play with, call Fred at wheeladaptor.com and get adaptors. In fact, the other day there was a guy on Turbobricks sellling a set of adaptors to go from our 5 x 108 to 5 x 114. Hmmm! Wonder what they were from...BMW???

Regards,
DS