If you want to model a thrown track on a Mk IV, you probably need to come up with a drive sprocket, idler and rollers. One idea for the running gear is to kidnap it from Airfix's Churchill tank in 1/76. The sprocket is easy to convert to an idler simply by grinding the teeth off and detailing and just detailing for the sprocket. The road wheels are the right size for the track rollers after thinning down. The difference in scale makes them just the right size for Emhars kit, but not quite as good for the Airfix Mk I (but still workable).
Wife does not understand me using this kit just for parts but at least it keeps me off the streets!