Sliding wood window
Hello,
Unfortunately, we can't be sure which parts would work for your window without seeing the original hardware. With that being said, the 5/8" diameter S500 spiral balances are commonly used with old-style wood widows. With that being said, you mentioned that the space in your sash is only 1/2", so you may need to use the 3/8" diameter S400 spiral balance if that is the case. If you think that you could adapt one of these balances to work in your window, you'll need to confirm the exact height of the visible glass in your window sash and add 3" if it's for the bottom sash and 1" if it's for the top sash to determine the balance length.
You would also need to weigh the sash and follow the chart under the product description to choose the corresponding tip color. See our installation guide here, as well as the list of compatible brackets under the related items section of the balance product page. Keep in mind that we can't guarantee that this would work but would be our best recommendation based on the information you've provided. Thanks for posting.