I was trying to figure out what souring a harness was, until I read further! You might try Olof at vintageimportparts.com, as well as swedishtreasures.com.
Alternatively, you could scrap the whole darn stock idea and get a shiny new streetrod kit from Painless Wiring. New, easy to find fuses, and circuit breakers available if you want! Just a thought, and probably heresy to some here on the 'board. My apologies in advance.