The Roco Panzer III is a very flexible model and makes for easy conversions. This model has had several modifications. The storage bin has been cut off of the turret rear. A good pair of sprue cutters will make quick work of this, afterwards a craft knife can be used to trim down any excess. A sanding stick in the 200 grit range will smooth off the rest. A small glass bead, sold at craft stores, was glued into the open space for the bow machine gun and a bit of wire glued in to make up the machine gun. The bead was glued in with CA glue.
Finally the tracks were replaced with the tracks from a large WWII German halftrack. A small number of these vehicles were tested and found to give better performance than the standard wheels, but were considered to be not worth the time and effort and expense to enter production. The tanks were then sent to anti-tank training school to teach soldiers anti-tank techniques. At the end of the war many were pressed into front line service.
Simply remove the standard Roco wheels and glue on another set of interleaved wheels. I used the tracks from a 1/76nd scale Eidai model halftrack, but the Roco SdKfz 7 tracks should work also.
Mike Bunkermeister Creek