Ribber balance

I need your help on this and I have attached three pictures of what I need. Sometimes it is hard matching these parts up using pictures alone. What I am looking for is 35 inches long and is a "ribbed" piece using a block and tackle operation. I measure the channel on the old piece and it is exactly 1/2 inch wide. The spring that goes on the inside of this balance is 18 inches long. I need this to have the little steel connector that attaches to the pivot shoe. My window weights 22 pounds (B code) and I need two of these balances. Could you please see what you have that comes close and e mail me so I can order them. I will probably wind up sending you one of the old pivot shoes, as you just have too many on your site and numerous dimensions.

yes on the vinyl tilt window. And yes I had already bought 2 35 series S770 balances. ( order # 616414) The 770 are squared off and not ribbed as pic #1 shows. Thus the squared off S770 fit ok but did not allow the window to slide up because of the squared off corners. The balances that I trying to replace HAVE to have the ribbed corners.
thanks