As far as I'm aware this is not a mod that exists, but wouldn't be awesome to have that a possibility?
I can only speak for myself, but every time I'm playing I bump into cars that have no parts(sparkplug, battery, radiator), wouldn't it be awesome to be able to go through car wrecks and find a battery here, a spark plug there, just something to help you get the car you found going!
There's already a chance of finding a good wheel, a hood or a door on a wreck, so why not allow us to take the items mentioned above from them as well?