After doing extensive research on the subject, here is what I have determined you'll need to correctly build Snowman's W900 (not K900, no such thing). Anyway, here goes. You'll need the AMT Kenworth W925 kit for the frame, hood, & sleeper. If you can find one with the tandem torsion bar suspension, that's a plus, because you'll need one of those, too. They are available from the aftermarket (Double Take Replicas, maybe?). You'll also need the cab & VIT interior from the Revell of Germany Kenworth W900 kit. For the engine, you can use the Cummins NTA380 from the AMT kit as some of the movie trucks had them, or you can pick up a Caterpillar 1693 from Kit From Services in England (he calls it the Yellow Engine). I do not believe the Snowman's truck has twin sticks for the transmission. In fact, I'm not even sure what type of transmission it had. Maybe Ben Wicker will know.
Good luck with your build.