Hm...Maybe I'm confused about something then. I was going to link to this thread:
viewtopic.php?f=14&t=34354&start=30#.Ucm4pzffLjY but I just saw you commented on it a few days ago. Will those Master Cylinders he cites not bolt up to G-body firewalls with his bracket (pictures in first post of that thread)?
It looks like he did his homework, but I haven't tried any of them and I'm still learning about braking systems. I'm looking to upgrade to the C5 set-up in my Monte and this whole "manual brake" idea piqued my interest so I can remove some clutter around my LS1. I'll have C5 discs in the front, Ford 9" drums in the rear and I wasn't planning on using a prop valve, since I'll still have the same disc/drum ratio. Any reason not to switch to manual brakes?