Rep Power: 0

Hello everyone. Looking for an answer to the best course of action as of now. My rear foot brakes have consistently been uneven. 100-130 on the left, and 220-230 on the right. I've tried bleeding, replacing the drums/shoes, bleeding again, replacing the cylinders and bleeding again, and still they're uneven. The parking brake is very close to even however.

Do you guys think I should try and clean out the rear proportioning valve or the brake lines? is there any way to test if the valve or lines are clogged/bad without losing all my brake fluid? Also, I can't find a proportioning valve to buy used or new where i'm at.