A basic way how to install this:

1.) Open OpenIV
2.) Search for "comet7.ytd" and click "Search "comet7.ytd" in all archives"
3.) Replace the new "comet7.ytd"

or directly go to

dlcpacks\patchday27ng\dlc.rpf\x64\levels\gta5\vehicles.rpf\
dlcpacks\mpsecurity\dlc1.rpf\x64\levels\gta5\vehicles\mpsecurity.rpf\

and search for "comet7.ytd"