Historical plates any cop problems ?

I have Utah Vintage Vehicle license plates on my 74 duster.
(your car has to be at least 40 years old for vintage plates)
So far I have not been pulled over by cops or highway patrol. In fact I received a "thumbs up" from a highway trooper on a patrol bike when he passed me. Then a few minutes later he pulled over some idiot ricer in a prelude because he was weaving in and out between lanes.

I even asked a cop about this, he said: "Normally it is not enforced but we do give out warnings a few times a year. There are not enough vintage vehicles around to give notice anyways. And sometimes we enjoy seeing them on the road, when they're being respectable drivers (no street racing)."
"We hardly ever give out tickets for them, the only exception is if your car has very visible pollutants coming from the tail pipe."
"If your car has a lot of white smoke constantly spewing from its tail pipe, its a hazard and you are to be cited with a fix it ticket."