I run my 1MP cameras at D1 resolution because most LPR software requires that the plate make up a certain percentage of the image regardless of the resolution. The higher the resolution, the harder the software has to work, the more CPU load it takes. On the other hand, I have an ordinary bullet with a 12mm lens and I get readable plates in the video at 50' day or night at 3MP, but that would not work with at all with LPR software but good enough for forensic research.
Not saying you will ever get LPR software, but to let you know that D1 is plenty of resolution to get a plate capture.
If you haven't bought the camera, the 3 best low light box cameras to consider are the 1MP Bosch Starlight, Axis Q1604 or Samsung Wisenet III low light box. Check with Wrightwood surveillance, they can order any of those brands for you.