Window sash

We should be able to help, but I will need clear photos of the balances in question. Specifically, I need to see the top end, bottom end, and whatever clip or hook is at the end of the cord.

Since the calibration of the springs are in question, we'd better get the weight of the sash, too. Note that the "sash" is the glass panel that the balances support, not the balances themselves. Knowing how much that weighs will tell me exactly how these springs ought to be calibrated. You don't want to just go up a weight grade because if the balances are too strong then you won't be able to close your windows. It's best to play it safe.

The piece in your photo is called a "top sash guide." We can help with this but I will need to see an undamaged version, if that's possible.

Thanks for your photos. Based on what I see here, you have either our S380-30 or S385-30, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

I will still need to see the top sash guide in undamaged condition in order to narrow it down. They all have flat tops, so knowing that doesn't really change anything. In the meantime, you can see our full selection here. 

Comparison of the S378, S380 and S385 balance shoes.

Assuming that all of those balances use the same nylon fittings, then you can use the same Series for each one of them. You should check, though. There's no guarantee  at all that they'll all use the same fittings. Better safe than sorry.