An early all-steel design, the Fox truck came into vogue in the late 1880s and stayed in use on non-interchange equipment (on mostly East Coast roads) through the steam era. At present, Fox freight-style trucks are only available in N scale from Panamint Models (by way of shapeways.com) -
Dimi Trains / Tichy Train Group also sells a Fox truck as part of their rotary plow kit (a truck which is presumably specific to snow plows) -
Fox - wheelbase 9.36mm, frame width 15.1mm, wheel size N/A (Use MTL 33" wheels), axle length N/A (Use MTL 33" wheels 13.7mm)