Swapping to front factory discs on my '71 Challenger. The drum brake brass proportioning valve seems to be standard across the board. When a car had disc brakes a coupler was added (for front brakes) and sealed with a copper washer.

I have an old brass factory disc proportioning/metering valve (it's toast) that I plan to use for reference and parts. I unscrewed the coupler to find a spring inside, and I thought I might have heard something drop to the floor when I pulled the spring out. I did find a lot of hard crud inside the spring, which continued to fall out as I cleaned it up. Is there anything else in there that may have fallen out like a ball bearing or something?

I guess I'm wondering if I can add the spring and coupler (and any other necessary parts incl. metering valve) to my original drum brake valve and make that work with discs, or should I just scrap it and buy a new repro?

Thanks!