Sandy,
For my 70RR resto, I ended up rebuilding all three valves. There's a good thread on this, but it's older than the new 2yr limit on searches (IIRC 2011).

Basically gutted all 3 valves and used repro kits/valve parts to rebuild. There's a guy in that thread that was selling kits. I was transitioning from DOT3 to DOT5 so had to clean them out anyway. For the metering valve, I used my date coded shell and rebuilt with the insides from a Fine Lines repro. Worked out well and kept my OE look. No leaks.