replacing old spiral balances circa 1940's

A contractor from north carolina says:
i am replacing dated spiral balances on old wooden sashes. original spring is 7/16 diameter, i'm assuming i need the 3/8. i'm looking at the series 400 because the bottom seems to be most compatable with what was there.

windows were held using a bracket very similar to bracket #14. i noticed that the description said these balances are used with aluminum windows. would these be strong enough to hold the wood sashes? they weigh 10.5 pounds each.

one is 24"s tall and the other is 23.5". will 24's work for both or does the 23.5 need a 23"?

and lastly, it is hard to tell from the picture but is the balance top ready to be screwed into the jamb or does it need a bracket as well?

any help would be greatly appreciated. thank you.
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Paul from SWISCO responded:
Thanks for posting. For wood windows going back to the 1940's, I recommend that you take a look at our S500-24 and see what you think. I would also recommend looking at either our 17-007 or 17-012 brackets.

Yes, the top of balance tube is screwed into the top of the window jamb and slides behind the sash.

Please make sure to take a look at our guide on how to adjust your non-tilt spiral balance.
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