I changed this rom "ww w.mediafire.com/file/jq7qzc0kuaow5xx/cm-13-20151101-UNOFFICIAL-p970.zip", but I did not test it,
Someone will test him for me?
Link = lgP970 cm13 marshmallow (no test).7z
This archive must be unpacked, then you have to pack two folders (meta-inf, system, and boot.img file) into a zip package. Now you can install rom.