Talk to any older engineers you can find or to various aluminium suppliers.
Having worked UK defence drawings, some of which dated back to the 50s/60s, every now and then I saw some fairly old and sometimes company specific specifications.
I was lucky to have a stress engineer well into his 50s who had 'seen it all' and usually knew where to look.
We have asked our suppliers but to no avail, This division of Fairy was based in Canada. Its an 8in dia tube we are guessing some type of agricultural callout. Finding anything this size is turning into quite a task.
If you've got some idea of the loads then you might be able to work backwards.
Or just pick a very high grade material. Although I'm not sure how certification would work.
We had problems of trying to make parts that had old material and manufacturing processes. We'd often end up re-designing the part for current materials and manufacturing processes. For instance rolling the tube and welding it or something in your case.
You could try and find out who that division of Fairy got bought out by but I wouldn't hold my breath for any help from them.
Sorry I can't be more help. I'm assuming you did web searches and got nothing, even on matweb.