I'm wondering why you're choosing to run disc brakes without a power booster. I doubt if I've ever seen a setup like that. Regarding line diameter, the only thing a bigger line accomplishes is more fluid in the line. once the system is bled properly the lines could be an inch in diameter without affecting the ratio of master cylinder displacement VS caliper piston movement. I'd choose a bigger diameter MC piston, and a small power booster that will still fit under the floorboard.
Jerry

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