You mean taking up a single expansion slot? I actually don't know of a R9 280X, R9 290X, or GTX 780 that takes up a single expansion slot. If I am misunderstanding the question, I apologize.
If you go a custom water cooling route, you can remove the cooler block and replace it with a custom water cooling block, then it'll take up one PCIe slot. It will still cover up two expansion slots.