The scenario supposes that the The Washington Naval Conference of 1921–1922 is wrecked by Japanese demands for parity, French intransigence, and Italian pride. These were all real issues that nearly derailed the conference, particularly on the part of France. A minor agreement is hammered out on battlecruisers and carriers, but nothing else substantial.
An attempt to try again in Geneva in 1927 also fails to get off the ground, but it does manage an informal agreement to a "battleship holiday", with no new ships started after 1927. This in turn is the groundwork that plants the seeds for the The London Naval Conference of 1930. It is here that the naval arms race is finally checked, and firm limits are set, although it has more to do with the world's economies being obliterated by the Great Depression than arms limitation.
A full treatise will come later, for what I seek now is anyone who has any info on Japanese shipbuilding infrastructure from 1920-1942. The best I could find was these threads:
Japanese Warship Construction by JWE
with this:

and
Alt_Naval IJN Fleet Data by Gary Childress
Does anyone have other sources I can look into?
Thanks,
Scot

