Window balance, shoe and pivot

This balance is not a standard setup and will have to be custom made. Before I go any further, can you tell me the exact weight of the sash that it supports? I'd also like to see a closer picture of the top end, where those rivets are.

The pivot shoe is a match for our 15-105 but the pivot bar is discontinued and no longer made. You may be able to use the 26-042 as a substitute, but I cannot guarantee that it will work.