I’m not finding much information on this or maybe there is only one type of 1942 4 door sedan. Is there a fastback model of the 42 four door? If so is it limited in production? Appreciate hearing back from you

 

According to my American Car Spotter's Guide 1940-1965 by Tad Burness, the fastback came out for the Series 61 in 1946. It then skipped a year for '47, but came back in '48 for the Series 62. I just don't know how accurate or complete the information is.