Thanks for posting. This looks a lot like our 15-192 Certainteed Pivot Shoe, and indeed that used to be what we would recommend. However, you have a specific version of this shoe, which was made by Simonton. As it turns out, it in fact requires a good amount of modification for the 15-192 to replace this Simonton shoe, and it can be quite troublesome to make work. Therefore, we recently started experimenting with alternatives. We now recommend the 15-259 pivot shoe, which should fit well in the track.
There's a catch, however. Because you're replacing the pivot shoe with a different type, I am afraid you'll need new Coil Balances as well, ones that are compatible with the new shoe. See the Series 159 Coil Balances, which are housed by the 15-255 Single or 15-256 Double Supports. To know what spring weights to select, look for stamp codes on the tongues of the coil springs. If there are none, or you are unsure, give me the exact weight of the window sash that these coil balances support, and I'd be happy to work it out for you. Note this also means you will need to replace the balance assemblies on both sides of the window.
Finally, to use this assembly, the original pivot bars would need to be replaced with our 26-089. We are still in the early stages of confirming if this replacement is a good long-term solution but we have high hopes that it will work with little need for modifications, if any. Take a look and see what you think. If you decide to give it a try, we'd love to hear how it works out for you.