Hmm, I was under the impression Victa manufactured all their own components, well, as far as chassis and 2 stroke engines where concerned, but maybe different plants, or perhaps they had a contracted company that took orders when demand exceeded their own capacity.
I'll start by checking those reall notices I have at home, if that shed's no light, perhaps we can see what can be dug up about Victa's different manufacturing locations during the period 1970 - 1974, that might give us something to go off.