Custom brush guard for truck

I went for semi-annual tech inspection for my Veryca and even I passed I was told better to remove my roof rack where I attach my LED lights.
So I asked guy if I can install front bull/brush guard, would it be legal? I pointed to another old Ford truck which was passing inspection at the same time and it had a bull guard.
So inspection station employees told me I need to modify my registration for this at DMV.

So I wonder can I install custom made brush guard or I need to install specifically designed for my truck if it’s available and manufactured?
What is a rules on it?
https://upload.wikimedia.org/wikipedia/commons/7/72/CMC_Veryca_van_left-front.jpg

Off topic but why does everyone say DMV? There’s no office that’s actually called DMV in Taiwan. That’s only in the US.

What would be your preference?

Motor Vehicles Office - MVO for short