Rigging wire size

So I am rerigging my hunter 30, having just rejoined the cherubini owners cult. The wires are quarter inch in diameter. I am going to be replacing the stainless steel rigging with galvanized wire and turnbuckles, 7x19 with thimbles etc. I read several different minimum breaking strength Notions regarding 1/4 inch 1 by 19 stainless steel. Does anyone have a guess as to what minimum breaking strength wire might have been specced for the late 70s? Or, conversely, has standing rigging wire gotten stronger for a given diameter since the late 70s? I am currently looking at a 5/16 galvanized wire with a minimum breaking strength of 8900 pounds which is substantially more than the 6900 lb that is supposedly the industry standard, though rigging only claims their wire is substantially stronger in 1/4 inch diameter ( I understand that suggested working load is different than minimum breaking strength). Why am I in galvanized? Because it's far less expensive and when the wire does corrode it is much easier to see and it tends not to sneak up on a person like stainless crevice corrosion does. Oh, did I mention rerigging the whole boat for about $240 in materials? Once again, is it likely that, through the manufacturing process or better alloying, that quarter inch stainless steel is stronger than was the norm back in the late 70s?

 

The attached is about 40 years old but might be start. Go back to your supplier and see if he can help. Keep in mind that 7 x 19 will stretch a bit more than 1x19