Hello, thank you for posting,
I agree that your original assembly looks to be a good match for the 15-087 pivot housing as long as the dimensions below match up.
It appears that your assembly only uses one coil spring. The 15-186 is for a double coil setup. If your original did not have it, you will not need it.
The coil spring is sold separately and you will need to install the spring in the housing upon arrival. Please review the S180-08 coil spring. One coil on each side will support a 16 pound window sash. We always recommend weighing the sash to make sure the weight matches.
Also review the 16-031 bracket if your original is damaged. Please review and let us know if you have any additional questions.
