I've just completed disassembly and rebuild articles for the GM 3905525 metering valve made by Bendix for 1967 - 1969 GM vehicles. I've also got a new seal kit available that I'll post in the classifieds. Here's the disassembly article:
https://www.musclecarresearch.com/gm-3905525-autopsy
The rebuild article:
https://www.musclecarresearch.com/gm-3905525-rebuild
I don't yet have a reproduction of the Bendix rubber dust cap. I'm exploring my options to see if it can be done economically.