Part numbers for #logicchips are pretty haphazard, but there are some patterns. That said, those patterns just make it more annoying that you can point to a part number and see how it would be the right chip for your #retrocomputer build, but that chip doesn’t actually exist. If only there were a 74X577 or a 74X239… if you see what I mean. Of course, if you can see those parts (574 with WE instead of OE, or 139 with active high outputs) anywhere else, please let me know.