Craig.....I have the Gavin Farmer book, "Great Ideas In Motion" published 2010 which covers Oz mopar 1946-1981 as well as a few other publications including the 1946-53 Workshop manual and 1954 Supplement together with both the 1957 AP1 Chrysler Royal and 1960 AP3 Chrysler Royal workshop manuals and from going thru the lot this may or may not help.........lol.........the production figures for Dodge are as follows
D49S 1954 1955 1956
/1 7 10
/2 1705 1318 833
/3 223 586 277
/4 91 941 654
Farmers book also mentioned that the D49 which was introduced in 1953 and continued up until the introduction of the 1957 Chrysler Royal had very few indentifiable styling changes, the main two appear to have been the deletion of the side trim or moldings thru the doors from 1955 and the adoption of chromed hooded headlight surrounds from 1956. As your car does have the moldings thru the doors it may have been a 1953 or 1954 built car however not sold new till 1955, but thats just a guess on my part............the other thing I mentioned regarding the engine choices and the confusion is borne out by the 1954 Chrysler Australia Workshop Manual Supplement which lists the 3 engines available as follows.......
D49 1/2 230.2 engine( with engine numbers after 243,000.......which would be the 23" Dodge/Plymouth engine)
D49 1/2 228.1 engine (with engine numbers suffixed "C"...........which would be the 25" DeSoto/Chrysler engine)
D49 3/4 250.6 engine (with engine numbers prefixed "Kew"......which would be the 25" DeSoto/ Chrysler engine)
I have not seen a 1955 or 1956 Australian Chrysler /Mopar/Dodge/DeSoto or Plymouth Workshop Manual, nor have I seen one listed but they/it may exist and have different info....did your car come with a workshop manual or owners manual?
It appears also that over over the 4 years that this series was in production a couple of other changes appeared.........pedals went from being floor/chassis mounted to being pendant or firewall mounted, also changes to whether it had a mechanical clutch to a hydraulic clutch as well as the introduction of a Oz made gearbox with selectors on the Oz drivers side of the gearbox and possibily the introduction of the parking brake on the rear brake drums tho' that may have come in only on the 1957 Royal with the 3 speed manual gearbox................anyway I hope this helps.............or confuses...........lol.............andyd