Worth investigating 2nd hand part sales, old parts do sell. Not something we can advise on in detail on this forum, but people with slightly older systems they are still running do need spares, and people build 2nd hand systems to save money, even if it is with older parts.
You'd connect it to the PC with displayport, as Nvidia GPUs don't do adaptive sync over HDMI anyway, and this would keep HDMI free for use with other devices.
HDMI 1.4 will support 1440p 75hz - I hooked up a laptop to my monitor via HDMI this afternoon to check and it was fine at that res and refresh. So it supports it in practice as well as theory