Great work David,
I am a firm believer that a dual circuit system is a safer bet. Jeeps of that era are not common here in Australia, but I am of the same mindset: Two circuits are better than one.
You are going to have to look at a servo to assist the braking as I do not think that the jeep system uses the large bore diameter like the C8 originally had.....SO (I think) your pedal pressure will be too high and you will need a right foot on steroids to push the pedal hard enough to work the brakes effectively. [One has a sneaking suspicion this thread will end up immortalized in Google] Perhaps you have re-bored the master cylinder to the larger diameter (I don't know) if so, the problem above vanishes...
Let us know how you go... we're happy to learn from your mistakes
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You can hide a servo easily enough.
I have actually rebuilt my original master cylinder, but it will be to get me mobile. I want to convert to two circuits.
Ian