Replacement Coil Balance system

So I have two windows that are the same size, they are both vynal double hung / tilt windows. One of the windows the previous owner removed both coil balances from the lower window so they could push it all the way up to insert an AC unit in the window. I am now selling and the new owners want it fixed but I don't have any of the parts.

So I pulled the coil balance out of the bathroom window that is the same size, for the bottom half. Attached a picture.

The window is 19 1/2 inches High by 27 inches wide, and it weighs about 11 pounds. The coil has a #7 on it. Do I have to buy the exact same type of coil balance, or can I use the S140 series you have on your site that looks like the complete system (all the parts).

If I can use the S140, should I go with the 5 lb or 6 lb L/R unit for a 11lb window.

If I need to get the parts, can you recommend which?

The issue is that there are no parts, they previous owner removed the coil balance system from the lower window and threw them away. The one I have a photo of is from a different window in the house.

So with that in mind, that I am replacing everything, should I still go with the individual parts, or can I just us a different system?

Also, the parts you listed, would I need two sets, one for each side of the window?