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The DeSoto Diplomat

Photos provided by James Benjaminson. Basic information from James Benjaminson and Bill Watson.

Long before the Dodge Diplomat known by most Americans today as the prototypical police car of the 1980s, Chrysler produced the DeSoto Diplomat - but only for people outside the United States. These DeSotos were, oddly, based on the American Plymouths, in the name game played so often, and so badly, by Chrysler Corporation. Thus, our first photo, a 1947 DeSoto Diplomat SP15C, based on the Plymouth P-15. While there is a distinct family resemblance in the lines, the grille and detail work is very different, providing a moderately unique identity.

Bill Watson noted:

The 1946 DeSoto Diplomat (and Dodge Kingsway and Plymouth) were the same in 1946 and 1947. In 1948 the main change was going from 16" to 15" wheels, and in Canada they also changed the compression ratio of the engine from 6,50 to 6.70. As well, the same car was sold as a first-series 1949 model in the U.S. So, not much changed from year to year.

The Australian Chrysler importer, Chrysler Dodge Distributors (Australia) Pty Ltd., imported the chassis with engine, etc., and had the bodies built by T.J. Richards Pty. Ltd., Adelaide, South Australia. Chrysler purchased Chrysler Dodge Distributors and T.J. Richards in 1951, combining the two into Chrysler Australia Limited.
The only sure way to tell a 1946 from 1947 from 1948 (and from 1949 in the U.S.) is by the serial number. Export Plymouths and their cousins were built in Detroit, Michigan and Windsor, Ontario. The DeSoto Diplomat were built with Plymouth serial numbers and modified model numbers (they put an "S" in front of the Plymouth number).
Land vehicle Vehicle Car Motor vehicle Steering wheel

Again from Bill Watson:

The American-built Plymouth used Chrysler's 'small' block flathead 6 with a 3.25" bore and 4.375" stroke for 217.8-cid. The Canadian-built Plymouth used Chrysler 'large' block flathead 6 with a 3.375" bore and 4.0625" stroke for 218.1-cid.

The November 2001 issue of the British publication. "The Automobile", shows a photo on page 61 sent in from a reader from Australia, It is captioned as a "US-built Mercury", but it is clearly an Australian market DeSoto Diplomat. The body has the "balloony" roof, slanted (and larger) front quarter panes, larger windshield, rounded side window openings in the doors, and rounded lower trunk edge.

But you can tell it is a DeSoto by the vertical bars in the grille, the DeSoto emblem on the trunk lid (above the brake light) and the "DeSoto" script just above the grille opening on the left side. There is another postwar Plymouth/ Dodge/ DeSoto beside it, but they do not show either the front or rear of the car. The DeSoto appears to have the emblem on the hood, although what condition it is in, I cannot tell. The caption says the reader found the cars on a farm in Cooma.

The Diplomat was not sold in Canada or the continental U.S. (it was sold in Hawaii prior to its admission as a state and also in Mexico, though).

From "A Plymouth By Any Other Name":

After the war (1949 to be exact) Plymouth converted its cars into three series of cars for both Dodge and DeSoto. The Dodges were the Kingsway, Kingsway Deluxe and Kingsway Custom while the DeSoto was the Diplomat, Diplomat Deluxe and Diplomat Custom. In later years, every body style Plymouth built was offered as either a Dodge or a DeSoto....

By 1959, with DeSoto sales falling like a rock, the export DeSoto finally received a real DeSoto front clip attached to the Plymouth body. All of this nonsense came to a halt with the 1960 model year. Plymouths were no longer disguised as Dodges -- but the new Dodge Dart now became the basis for the DeSoto Diplomat -- with little more disguise than a few pieces of chrome trim and the nameplates and hubcaps. Dodge also provided the basis for the 61 DeSoto Diplomat. How many were built is unknown but its possible it equaled or even exceeded production of the real DeSoto!

Serial numbers (from Bill Watson)

The SP15-S was the DeSoto Diplomat DeLuxe and the serial numbers were -

Detroit :

1946 : 15 154 001 to 15 206 935

1947 : 15 206 936 to 15 252 278
1948 : 15 252 279 to 15 292 209
Windsor :

1946 : 9 624 461 to 9 631 185

1947 : 9 631 486 to 9 650 874
1948 : 9 650 875 to 9 664 000 and 9 510 871 to 9 516 548
For the SP15-C, DeSoto Diplomat Special DeLuxe :

Detroit :

1946 : 11 496 001 to 11 643 103

1947 : 11 643 104 to 11 854 385
1948 : 11 854 386 to 12 116 123
Windsor: Same numbers as the SP15-S DeLuxe

Just as a point in interest, the U.S. market 1949 Plymouth DeLuxe P15-S was [serial number] 15 284 535 to 15 292 209 while the Special DeLuxe P15-C was 12 066 020 to 12 116 123. The 1949 numbers were used only in the U.S. The rest of the world did not offer the 1946-48 models as 1949 models, but waited until the introduction of the totally new P17 and P18 models.

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