Re: Is there a bracket that can be used to install new light fixtures in a smaller bo
If it's the kind of box that lacks a pair of threaded tabs a the edge, it will instead have a female threaded hole at the center. You need to get the right threaded nipple and then a threaded bar adapter to fit a two-hole fixture to that kind of early box.
Occasionally the box will have a built-in nipple with outside threads, with the wires emerging through this hole; you then use an adapter known as a "Hickey" to attach the nipple and a bar adapter as with the other style.
Remove not the ancient landmark, which your fathers have set.