Hmm. First make sure your current hardware is good. You should already have the bigger master cylinder (the bore on the older ones like mine is smaller)... check your rubber lines, replace the master/booster if they're suspect, bleed the hell out of it, etc.
Depends on how you drive, I suppose, but my '74 (all stock brakes) will lock all four and skid if I slam the fat pedal. (Great way to make passengers s&&t themselves /forums/images/graemlins/smile.gif)
Anyway, not to dissuade you, but make sure everything else is new and shiny 'fore you go upgrading.
-- A