Part 1. [Installation]
1. Go to /Grand Theft Auto V/mods/update/x64/dlcpacks
2. Drag and drop 'm113k' folder into path 
3. Go to /Grand Theft Auto V/mods/update/update.rpf/common/data
4. Right click dlclist.xml > Edit and add the line <Item>dlcpacks:/m113k/</Item> to the end of the Item list

Part 2. [To change any car's audio to the m113k]
1. Go to [insert any addon car name] file location > dlc.rpf > data > vehicles.meta
2. Right click > Edit vehicles.meta
3. Change audioNamehash line to <audioNameHash>m113k</audioNameHash>