It is lot of extra time to maintain those outdated drivers. Why not try with the Nouveau drivers?
Based on the PKGBUILD the file of 340.108 drivers should have a sha256sums of 995d44fef587ff5284497a47a95d71adbee0c13020d615e940ac928f180f5b77
You can also get the DKMS driver file from here: Release 340.108-1 · philmmanjaro/nvidia-340xx-dkms · GitHub You also need to install the proper linux-headers like linux54-headers or linux419-headers, depending which kernel you are using.