All the assets go here, perhaps like

* GameData/Assets/Common/
* GameData/Assets/Common/Endcaps/...
* GameData/Assets/Engines/125m/...
* GameData/Assets/Engines/
* GameData/Assets/Engines/25m/...
* GameData/Assets/FuelTanks/
* GameData/Assets/FuelTanks/375m/....