You got it Crius,
This is what Matomart sent me,
If your tank had the plastic engine, and you want to use the metal tracks,you will need to upgrade the engine. In other words, to support the metal tracks, you would need the metal engine. Metal tracks will not support the engine. They will only add weight to the engine. To support the plastic tracks,you can keep the plastic engine and use the metal engine as upgrade part.