Funky, are you sure they're different enough structurally? Isn't it just a wagon version of the sedan? I was seriously considering this myself a while back, but then I read this in the SEVS Register Application info:
2.2.6 The following variations by themselves, DO NOT constitute a different Model:
(a) trim or optional specification variations;
(B) body variants, such as Sedan, Hatchback, Station-Wagon or Single and Double Cab, or with Sleeper-Cab, of the same basic Model;
© wheelbase or wheeltrack variations;
(d) goods carrying bodies, plant and/or equipment added to a vehicle, usually a chassis-cab that has minimal effect on ADR compliance;
(e) variations in profile being a result of the addition, or modification of Air Dams, Skirts, Spoilers, Wheel-Arches and similar;
(f) different engines and/or transmissions, including petrol or diesel, manual or automatic, or 2WD, 4WD or AWD, turbo-charged, supercharged, variations of fuel injection technique (eg GDI) or Traction control.
Personally, I reckon that rulings b and f suck, cos I'd love an IS300 wagon with 4WD.