Included in the zip are four sounds, hornstart, horn, hornend and radio. Also included is a simple readme and soundscript. The zip is quite large mainly because the horn loop and the radio loop are respectably long.
Here is a Soundpack for the 5.9 Cummins in a Ford School Bus. You are more than welcome to use these sounds, but please give credit where credit is due.
This has been used in vehicles in version 0.38 and higher, so I know it will work.