to install this mod do the following
go to this directory: C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\HIS\Hanover
locate the file "HanoverAssets.ap" and unzip it
copy the contents of the "HanoverAssets" folder created in the previous step
paste them here: C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\HIS\Hanover

if you have my SD40-3 Mod you can skip to these steps
navigate to: C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\HIS\Hanover\RailVehicles\Diesel\SD40-2\Default\Engine
paste my edited file and click yes when prompted
Enjoy!