Not finding 10" drum spring for 67 GTS

I don't know what the big deal is, It's a spring and it has the power to pull the shoe back. Over the years the cost of making a spring that is not needed, so they got rid of it. Same spring for both shoes. If you can prove to me that the short spring is better than the long spring than I will agree with you, It's just a spring and it pulls the shoe back and that is it period.

"Drum brakes have a natural "self-applying" characteristic, better known as "self-energizing."[4] The rotation of the drum can drag either one or both of the shoes into the friction surface, causing the brakes to bite harder, which increases the force holding them together."
4 - The AA Book of the car, 1976