unfortunately it's not quite that simple, but if you have crappy shoes in the front, or ones that are for road racing etc, then yes, pads with higher initial grip when cold will help.
if it takes an unusual amount of force to lock the brakes in general with the power booster, then you need a smaller master or a higher power booster as well.
also, i'm not positive how the gm prop valve system works works and this may be contributing to the problem. i would have used a 69 or 70 ford prop valve setup.