I'm no expert, but from what I've read on the subject, they seem to be a more or less "aftermarket" item. It seems that early on, the units were delivered with very minimal grabs on the front end, but after owning them for a while, many railroads started installing grabs in strategic locations to make maintenance easier and safer. The exact style and placement often varies from one rr to another. Not sure if EMD eventually installed grabs at the factory, or if the rr's continued to do their own.