After WWII, Packard produced a new line of flathead design six (model 1M-245) and eight (model 1M-356) cylinder marine engines based on the automobile versions and the experience gained from the war production. Of the 1M-245 type engines, only 1,865 were produced between Spring 1947 and January 1951, with only a handful survivors. Of the 1M-356 type engines, approximately 1,525 were produced between 1947 and 1950. Even more rare is the experimental "R" type racing versions (1M-245 "R"), of which only 10 were produced with currently only one known survivor, a 1M-245 R six-cylinder engine powering today a 1936 Gar Wood Speedster.