Here is a Z scale SW1200 shell and frame. This is an alternate to the generic SW1200 model. It has details unique to Southern Pacific SW1200s. To power this model, use the motor, trucks and circuit board from a Rokuhan Shorty Motor Chassis B (sold seperatly).
You will also need the following:
Trucks & fuel tanks sold here
Handrails and decals sold here
Rokuhan Shorty Chassis B (available wherever Z scale model trains are sold).
Instructions to assemble it are here; http://www.thezmaker.com/