In California if the vehicle weighs under a certain amount (for some reason 2,100 #,s is sticking in my head) you do not have to have fenders. That is why you see T-buckets, some Highboy Roadsters, Motorcycles, and utility trailers with out them. The guy that owned the T-bucket I helped build had a certified weight slip in his wallet and glove box just for that reason.
so I am going to go to Kommiefornia and rock my truck as just a cab with an open header (with a cat for the feds) on the engine
Bring it on in if you want to be an idiot, they will write you up or impound.