I picked up a hydroboost from the junkyard this weekend. The junkyard didn't have any first gen Astro vans so I ended up with a unit off a 2008 Duramax. I'm converting from manual drum/drum to hydroboost with front discs, but what master cylinder and proportioning valve do I need? Can I reuse my stock master cylinder? I'm assuming the drum/drum proportioning valve isn't right for a disc/drum setup. I measured the bolt spacing on the hydroboost to my stock master cylinder and they appear to be the same.
This is in my 68 GMC C15 2WD.
Pics of my stock setup and the hydroboost:
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