[GM72K10]

For sale recently on ebay, item 2400908844, were 2 68 GM headlamp bezels, I didn't buy these, but by coincidence have the same thing, Group 2.728, part numbers 391747 Left and 3917468 Right. Can't find them in my parts books. Anybody know what they are for, a tilt cab maybe? They are heavy and seem to be cast. Thanks!