Hello! These old Certainteed parts aren't made anymore, but the modern equivalents will work for you just as well with a few minor alterations.
Starting with the pivot shoe, see our 15-192. This is going to be the biggest issue since Certainteed now makes these with alignment lugs on the front face. Your old shoe lacks these and the window track wasn't made to accommodate them, so if you try to install the 15-192 as-is, it won't fit. The simple solution is to just cut them off. The parts related to this are the Series 170 coil spring, 15-156 cover, and 15-157 drum.
If you needed a new pivot bar, see our 26-175. This looks very different compared to your original at first glance, but this should install in your window the same exact way and interact with the new 15-192 without issue.
Please let me know if you had any other questions. You can review these products on their respective store pages, linked in this post.
Windows don't really come in standard sizes, unfortunately. This is a case-by-case kind of thing. If you don't have a stamp on the old springs then your only other option is to weigh the sash on a scale and extrapolate from that.
The formula we use is to divide the weight of the sash by how many springs support it. Looking at your photos it appears that you have one spring per side, so you'd simply divide the sash weight in half.
These are very precise systems, so you never want to guess at weight. You've already seen what happens when you get it wrong. If the spring strength is off by even a few pounds, it's not going to work right. You need to be as exact as possible.
If you were to tell me your sash weight, I'd be happy to make a recommendation. Just let me know.
For a 13.4 sash, you could use our S170-407. These carry 7 pounds each, giving you 14 pounds of total support. That's a bit over your original but it should still be okay. That kind of difference won't be the end of the world.
