Steve and group:
I spent a fair bit of time trying to sort out the three series of wooden Swift reefers that were covered by the three variations in the Sunshine kits -- the 2500, 5200, and 6700 series, all of which are referenced in Martins Feb 1993 article. My goal was simply to understand the genesis of these three series to facilitate accurate modeling, so I did not really delve into other significant groups such as the 3300-5199 series. I relied mostly on my collection of ORERs that tend to be in ~5-year increments (1926, 1930, 1935, 1940, 1945, 1954).
ANAICT, the 5200 series dates to about 1931-32, and retained its original numbers into the 1950s. Some very similar cars appear in the ORERs in the same period: the 500-699 series that appears in Martin's tabulation, and the 1900-2499 series that does not (presumably due to renumbering).
The 5200 series doesn't appear in my ORERs until 1945, and may have been closely related to the 3300-5199 series, Martin attributed these cars to the "late" 1920s, and my best guess is that the were originally numbered in 17400-19999.
The 6700 series purportedly dates to the mid-1920s, but again these numbers don't appear until 1945. I had a lot of trouble backtracking this group through the ORERs, and really couldn't identify a likely series for these cars prior to 1930. In the 1935 and 1940 registers, these cars may have been in 12700-15799.
My experience suggests that It will not be easy to construct an accurate time-line for the Swift roster, especially if the ORERs are the principle source of the data. I have a few photo that help a bit, but am not aware of any company records that would shed better light.
Hopes this helps.
Swall Meadows, CA