Unfortunately, part of the upgrade process will involve the fitment of...wait for it...330mm rotors/4-spot calipers on the front, thus rendering the 15" rims "obsolete"...Frankly, I'm happy enough to use the existing road tyres (LM702s) for the occasional track-work I'm likely to do. Not the best grip, but "adequate" for my ability.
That said, I am still going to need a 17 x 7 rim in a (35mm, I think) off-set to use as my new spare. Anyone have one of these lying around? (Must suit an MX83 Cressida).