Randy's right, Mopar was late with the '49 redesigns, so the '46-'48 Dodge design was also sold as a '49 model for several months. I recall reading that it was until February, but I'm not at home to consult my source. If your title says it's a '49, treat it like an early '49.
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.
It has happened many times before. New body was not ready at model year changeover. Timing was quite rigid in those days. Dealers planned a big model rollout. Every dealer planned a party for regular customers.
Agree with everyone here about the '49 issue. Just make sure the number listed on the title matches what you can ID on the car/body/motor. In MI, my Desoto is titled as a Chrysler because Desoto wasn't recognized any longer by the Secretary of State (DMV) in the late 80's. It is also titled by the motor number and not the body number found on the door. I've also found during the restoration that the motor number corresponds to the frame ID number. The frame ID is stamped on the top side of the frame under the trunk area on the driver's side almost opposite of where the spring jounce bumper is. You'll NEVER see it unless you take the body off of the frame. I would also caution you or the new buyer, if the car is titled under the motor number stamped on the side of the block that IF you (new owner) has the motor rebuilt to make sure they do not grind the motor serial number off when they're doing the machining. Since it's a flathead block, it's very easy for them to grind that number right off as it's so close to the main machined surface. I had to have my guy pay special attention to that when I had mine done. I hope that helps.