I'm not an automobile historian, so I have no clue about this, but when Sonny get's killed at the toll booth the windshield of his car breaks like regular glass when it's shot. However, when Carlo is getting strangled and kicks the windshield it cracks but stays together like safety glass.

I was wondering at what point did car companies start using safety glass for windshields? It seems to me that this could be an anochronism in GF, but then again a bit of time had passed between the killing of Sonny and Carlo so I don't know.