Well, when i measured mine up for carpet, the space between wheel arches was 125 cm front to back and 92cm wide, thereabouts.
Although the front to back measurement is measured right at the lowest point. Don't forget that the bulkhead isn't vertical at the bottom, it's tapered up to the wheel arches. The length of the wheel arch is approx 117cm. So if you put a big box in the back, it would need to fit inside 117 x 92 cm.
Hope that helps. Im pretty sure your c-f reg station wagon would be the same dimensions as my L reg hardtop.