If I go to 17", is it really 7J what is the widest possible? I have ASA AR1 wheels on the TVR Cerbera and i Think they would fit the Mantara nicely. They also have the correct offsets.
I have a 1999 Marcos Mantaray (see profile pictures) with 17x7 front and rear. I believe the offset is ET35 and have 20 mill spacers on the front only to avoid rubbing on the inner arches. Hope this helps