To install this mod
locate this Directory: C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\RSC\SD70MSPPack01
Unzip the file called: SD70MSPAssets.ap
copy the contents of the newly created SD70MSPAssets folder
paste the contents here:  C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\RSC\SD70MSPPack01
copy my mod and pase Here: C:\Program Files (x86)\Steam\steamapps\common\RailWorks\Assets\RSC\SD70MSPPack01\RailVehicles\Diesel\SD70M\Default\Engine
Click Yes and You're done!

enjoy the large selection of numbers!!