Krazeyone, thanks for the feedback. Good thing is that almost all g-body cars from 1978 to 1988 are set up from the factory to accept manual brakes. The hole is drilled in the pedal, so all you need is a plate to cover the firewall, an adjustable pushrod, and a retention cup to keep it from falling out the back of G-body 7/8” bore manual brake master cylinder. Problem is now most rebuilt calipers may be of the quick take up (low drag) variety and are problematic (won’t have the volume) when using a strait bore master like the 7/8” bore g-body master cylinder. A step bore master cylinder is required for those brakes and, in my opinion, have to large of a bore at 24mm. I assume your calipers on your 50 and 57 were part of a kit, so they, more than likely, would not be quick take up (low drag). But if you bought them at the auto parts store, they may be the low drag type, because these calipers where used from 1978 to 2003 on G-bodies, 3rd gen F-bodies, and S-10 Trucks and SUVs. Most of these cars from 1981 on came with the quick take up (low drag) calipers. Do the auto part store’s suppliers rebuild them with out the quick take up design? I have not idea, so that is why I would always go aftermarket when using a metric caliper.
I believe the problem I have now is caliper deflection and or a pad that requires more heat (FF rated) to work. The bore size of the caliper is only an issue if the MC doesn’t have the fluid volume to make it work. With an increase in bore size and piston area, I should see an increase in clamping force. I am going to try the 2.75” big bore Wilwood metric calipers and test to see if my 7/8” bore master has the volume. If it does, and I don’t get the braking I want, I will then change to a different (EE rated) pad.