For many many years, you were prohibited from using the vehicle in any capacity other than shows, events, or "occasional" pleasure driving. Oh, and to and from a shop. But there was no penalty clause in the law. So you could do anything that you wanted on historical tags and the most the state law enforcement folks could do was to inform you that you weren't allowed. But no tickets could be issued because there was no penalty statute.
That all changed two years ago. Now, it's a $140.00 fine for towing a trailer with a vehicle bearing historic plates. Ask me how I know. And then I got stopped by a different State Trooper the following day. It wasn't that hard to get the truck through inspection. And I got it taken care of quick.
Now I suppose that it may be easier and cheaper to put that $140.00 towards parts for repairs and get regular plates.