Yes, I've tried looking this up. I've found basically nothing. Everyone I've found that does a manual brake conversion is either in an L-body and/or using the 10.25" brakes because they drag race and are trying to loose weight.
I've been trying to do some math to see if aftermarket racing type master cylinders or entire pedal assemblies can be used with the stock 11" brake system. So far it's been a lot of measuring and figuring, but no real conclusions as I haven't taken the calipers apart (and really don't want to).
My best guess at the moment is that due to the stock pedal ratio (3.3 confirmed by physically measuring), the pressure required for locking the brakes (this is a requirement because if you can't lock them, you don't have enough brakes), and the volume of fluid required to actuate the stock single-piston floating calipers just don't play nicely with a manual brake conversion.
If anybody out there has done this, or knows of somebody that has done this successfully, I'd REALLY like to know. I would love to get that gigantic brake booster out of the way!