got your email..
the shop owner is technically correct...
the diameter is thus that the radius is waaaay off from OEM...
your speedo will be way off my friend....
best fit is probably 215/45x17 - which equates to about 626mm rolling radius.
OEM - 205/55/16 = is a rolling radius of 633mm
the ones you're after - 215/40x17 = 606mm
see the difference here???
also, be sure to go with a wider wheel.. 7.5" would be best...
hope this makes some sort of sense.
buying wheels/tires and getting it "right" is a big headache.

Jamie