I have been experimenting with the v1.4 777-300 and 777 Freighter Expansion Models in P3Dv2.2 and they are working fine.

Here is what I did:

I copied the CS_B777-300_PW, CS_B777-300ER_GE and CS_B777F folder to P3Dv2.2
then I modified the CS_B777-200ER_GE and CS_B777F panel.cfg's so they would work in P3Dv2.

Those of you only using P3Dv2 might need to install the Expansion Models using the Migration Tool, but you will still need to modify the panel.cfg's.

I have made the panel.cfg available from my dropbox (it contains the modified panel, panel.cfg, and a backup of the original panel, panel_original.cfg). Download it here: https://www.dropbox.com/s/cfg3vf6vmvxh89m/773%26777F_P3Dv2.zip
Just extract to the Prepar3Dv2\SimObjects\Airplanes folder and allow the panel.cfg to overwrite you current panel.cfg

Note. The panel.cfg for the CS_B777-300_PW is aliased to the panel.cfg of the CS_B777-300ER_GE, so it does not need to be modified!