SOLVED! (kind of)
I was getting kinda fed up with this problem. So I booted into windows and used the Custom Resolution Utility to modify my monitor’s preferred resolution/rate to the one I wanted and exported the custom EDID file. Then I followed this guide to make the graphics card use the custom EDID file.
However. If I added the option to /etc/X11/xorg.conf.d/99-nvidia.conf like @cscs explained, it did not take effect. But if I add the option to the Device section in /etc/X11/mhwd.d/nvidia.conf (which I probably shouldn’t be doing) it did actually work and used 74Hz as soon as I rebooted!
Did I somehow break the functionality of xorg.conf.d? Should I be using mhwd.d instead and cscs just switched them up by accident?
So yea, basically: Trying to make the graphics card allow custom resolutions that were not on the EDID info did not work. But generating a customized EDID file that allowed for that custom resolution did work.
If anyone knows of a good EDID editor available on linux, please lmk in this thread.