Unfortunately, the bulletin that likely applied to this issue is not available on the mediacat, but this one is, which mentions the 0000 400 1300.
The bulletin number that likely applied was #22.1990
My dad was an electrical engineer that specialized in transformers. He came up with material to put in the oil to conserve oil in the 1970s, during the oil crisis.
Looks like several sellers in the US have the springs.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2323012.m570.l1313&_nkw=0000+998+1400&_sacat=0