FallenEclipse on YouTube is where I got the list of codes from.
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Put the save file in This PC > Documents > My Games > Borderlands 2 > WillowGame > SaveData > 76561198028988149 Then load up your game, press start with "Axton The Head Whore". Once you get through CL4P-TP's little cutscene, open your inventory and use all the head skins.
I used Gibbed's Borderlands 2 Save Editor (Revision 256). Thanks to FallenEclipse (https://www.youtube.com/channel/UCGtOdpobMphW7JVSiyj1GiQ) on YouTube for the list of codes. I simply went through and put them all on a save file. If wanted, I can do one with skins too.