Part of the reason for building a car is self expression, and as such that brings a touch of art to the equation. The origins of hot rodding are based on performance, and the biggest contributor is the engine. For years rodders left off part or all of a hood assembly to show off thier "bullet". That's my long winded rationale for why I really dislike firewall mounted master cylinders, and power boosters even moreso. They are a major wort on what should (and can) be a pretty face. Some will whine "Its about go, not show!", but if you're building the car one doesn't preclude the other (a point that some narrow minded folks don't get when they think a well turned out car is a trailer queen when in reality it's driven).

If you like a swing pedal, and/or have limited under floor space on the frame, take a look at some full size Dodge vans. They have an under dash booster/m.c. unit, similar in design to the after market one made by Kugel http://www.kugelkomponents.com/produ...akesystem.html They're a little bit of a pain for checking the fluid level, but in a good system that's not a frequent requirement.

Under floor systems are made by many suppliers, and as Dave said, you want a proportioning valve, as well as residual check valves. Here's a nine page article that will probably tell you more than you want to know; http://www.hotrodheaven.com/tech/brakes/