Okay. I usually never mess with putting cars in the x64's because when i put them in the latest patchday, they work.
Dont extract anything. You're using a mods folder, so if they corrupt, you can go into the vanilla update and get the vanilla cars, so ignore those steps. Do this:
Go into x64e, vehicles.rpf like it says, and drag and drop the new police2 into there. Do the same in patchday12ng, just to be safe. That should work. Hopefully... I dont deal with x64's, like i said. Also, drag and drop the handling.meta into the spot it says. Dont back it up.
(like i said. If doing any of these steps causing anything to break/corrupt, simply go into the gta v directory, and go into update, instead of mods>update, and drag the vanilla file to replace the modded file)