I've got this set of used Kumhos for sale:
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/767021-kumho-17-tires-sale.html
(2) Kumho Ecsta SPT, 255-40-17
(2) Kumho Ecsta MX 225-45-17
FWIW, the overall diameters (25") are equivalent to 16" counterparts (205-55-16 and 245-45-16). Other than radically different wheel offsets, you shouldn't run into any OD interference or ride height issues.
Sherwood