Chrysler Corporation's 1948 models became 1949 models on December 1, 1948. The last of these 1st series cars were built in January, 1949, although the last of them were shipped to dealers in March, 1949. Not surprised it took Chrysler a couple of months to clear them out.
The new 2nd series (REAL 1949 models) went into production in February, 1949. Plymouths went into production in the 2nd week of February.
This applies only to Chrysler in the U.S. Chrysler Canada built 1948 models through to the end of December and shut down the plant. Thus no 1949 1st series in Canada. The 2nd series went into production in February, 1949, and thus the Windsor car plant sat idle for a month. The truck plant, though, was busy through 1948 and 1949.