Try using 2.2.1 for latest release that works with 1.5.8.5. also sometimes when you unzip with Windows' default unzipping system it can make a folder inside a folder with the same name so make sure you only have one folder called MorePartsMod with the rest of the assets, settings, and dll files inside. There should not be a folder within a folder. Yo fix this simply go in the first folder and click the folder inside of it and cut and paste it outside the first folder. Sorry if it's a bit confusing but hope it made sense.