For 1949, Mercury introduced its first postwar model line. The first Mercury of the combined Lincoln-Mercury Division, the Mercury Eight now shared its body with the Lincoln (instead of the Ford). Keeping its 118-inch wheelbase, the Mercury was sized between its two divisional counterparts. In place of the updated prewar body, Mercury adopted a "pontoon" body, ending the use of running boards entirely, along with separate fenders. The 239 Flathead V8 was carried over, producing more power than in its Ford counterpart. 
In a change to the model line, the four-door station wagon was replaced by a two-door model; the design of the wagon body structure had shifted to steel, relegating wood to body paneling (still manufactured at the Ford Iron Mountain Plant). An 8 tube AM radio was introduced as an option; full instrumentation was added to the dashboard. A new overdrive system was optional, activated by a handle under the dash.
The shift of the Mercury to the Lincoln body proved successful; alongside its Ford counterpart, Mercury broke sales records for 1949. 
For 1950, the Monterey name made its first appearance, as Mercury introduced a high-end two-door coupe, similar to the Ford Crestliner, Lincoln Lido, and Lincoln Cosmopolitan Capri; the Monterey was intended to compete against the two-door hardtop coupes introduced by General Motors in 1949. The front suspension was independent with stabilizer bars. For 1952, as Mercury redesigned its model line, the Monterey was established as a stand-alone nameplate, with Mercury renaming the Eight as the Mercury Custom. Within its era and beyond, the third-generation Mercury Eight was popular with customizers. In 1949, Sam Barrisbuilt the first lead sled from a 1949 Mercury Eight; the Eight became the definitive "lead sled", much as the Ford V-8 (as the "deuce") was becoming the definitive hot rod. The Eights were among the first models to receive an aftermarket OHV engine swap, since Oldsmobile and Cadillac developed the first high-compression OHV V8 engines in 1949, whereas Ford was still using a sidevalve engine. Sam and George Barris also used the 1949 body style to build "the most famous custom car ever", the Hirohata Merc, for customer Bob Hirohata in 1953. Setting a style and an attitude, it had a "momentous effect" on custom car builders,  appeared in several magazines at the time, and reappeared numerous times since, earning an honorable mention on Rod & Custom's "Twenty Best of All Time" list in 1991. The Eight remains a very popular subject for car modellers. In 1990, Mattel Hot Wheels created a model of 1949 Mercury with a chopped top. It is called Purple Passion.[citation needed] Fiberglass replicas of the Eight, inspired by Sam Barris's car, are still in production and are popular with custom and rod enthusiasts.