The deal was, the 42 model year went into production at the normal starting time, around Aug-Sept. Though the USA wasn't officially involved in the war before the Pearl Harbor attack, a few companies were producing war items for England. After the attack at P.H. The USA got officially involved and most production facilities switched over to the war effort. Most 42 model year vehicles were the ones produced before the attack. Some automobile and truck production continued through out the war, but those would have been 4 door sedans and trucks deemed necessary for delivery of production supplies.
Towards the end of the war, civilian light truck sales and production began on a limited basis for farm and business use. Full production of cars and trucks presumed as the war ended. As one would expect, demand was high because the old cars & trucks were pretty worn out, and a fresh batch of service men was returning with money to spend. Once production ramped up, most new vehicles were considered 46 models.

So, 41 was the last full year of auto production. 42 production was in full swing from Sept until December. Anything produced (and likely everything sitting in stock) after Dec 6 was likely military bound. Limited civilian sales occured from Dec 42 until early or mid 45 with full production kicking off at the war end as 46 models. The 46-48 models were shipped out as fast as they were produced with many companies changing the model year only because of the date the vehicle was produced. It was into the production year of the 48 models before updates other then very minor were to take place at most companies. By the 49 models, most were of new design.

Dates may be off a little one way or another, but this is generally the way it went down. Gene