have you considered going to an under the floor power booster? There are several kits available that use a small diameter vacuum booster mounted in the same position as the current master cylinder, inside the frame rail. You don't necessarily have to do the whole dual line conversion- - - -disc brake setup- - - -just add a small diameter vacuum booster, shorten the pedal height, and use a slightly larger diameter master cylinder bore to compensate for the shorter pedal travel. The power booster will compensate for the increased pedal effort created by a bigger bore MC.
Jerry
