[bobcowan]

13" should be enough to run a brake booster. Especially if you have a resevoir.

The current pedal ratio is good for power brakes. 6-7:1 is just about right for manual brakes.

Your MC bore is probably too big. A bigger bore will move more fluid, but it takes a lot more effort to create pressure. You might do better with a smaller bore, more like 7/8".

The downside of a smaller bore is that it takes more movement of the pedal pad to make that pressure. And increasing the pedal ratio will do the same thing. But you gain the ability to modulate the brakes easier; the pedal is less sensative. It's a trade off.

You also need to take a look at where the brake rod attaches to the pedal. That pivot point moves in an arc. If at rest the pivot point is at, say, 6 o'clock, as you press the pedal, it moves in an upward arc, towards 9 o'clock. The further you depress the pedal, to less actual MC plunger movement you get.

To be the most efficient, the pivot point should be at about 3-4 o'clock at rest. If you change the pedal ratio, consider adjusting that pivot point - if needed.