I visited a nearby place that restores and sells parts for British sports cars, and I picked up a used Spitfire windshield for $75. I took it home and cleaned it up, removing all the old grime and sealant around the edge. Then I cut away the gasket to remove the original windshield, which I had managed to bust after I had successfully re-installed it after painting the car. By now I’ve gotten pretty good at installing these windshields, and I got the new one in place in about 30 minutes.
Once the windshield was installed, I visited the Motor Vehicles office to get a replacement Collector Car inspection sticker (the old one was of course on the old windshield, and was about to expire anyway). But they told me that my car was no longer eligible for the “Collector Car” program, and I would have to apply for the standard “QQ” historical license plates. So I went home, filled out the correct form, and sent it (with a couple of photos of the car and a check) to Trenton.