These keyboard mounts are in great condition and should work perfectly in my 64C case with either the vintage motherboard or the U64 Elite II motherboard.
The price was great, and the mounts look good (which normally doesn't matter, but this is an engineering test system, so the keyboard will be exposed.)
A note: use heatset nuts, rather than screwing directly in to these mounts. The mounts will be more durable that way, since 3D printed material tends to split easily.