I am doing FudgeMuppet's Mad Max build, and I have all of the items that they suggested....only there is one issue. I cannot figure out how they got the Metal arm to look like that, and Google is of no help. Does anyone know the armor modification, or combination of those armor modifications, that were utilized to get the arm to look the way it does? (Pictured)

I can't say for sure but unless he has a texture mod it is likely that he simply modded it in game using a armor workbench. Try changing it to the shadowed variant, I never really used that particular armor so i am unsure of how it changes visually depending on the installed upgrades.

@SL3V3N Thank you for the suggestion, but I found it. It's actually the Heavy Operator's Right Arm from Nuka World.

Cool, glad you found it.