I had 4whl ( non-power) drums on my 69. They always worked good enough on the street but the first time on a road course they scared the hell out of me. So what I'm saying is it depends on your use. Front disc brakes will always be a good idea just for safety sake but they may not stop your car any better if you don't really put them under undue stress. But can you count on that? I agree that it probably will not change your trac enough to make a difference for your rubbing issue. Tire size and back spacing is what it takes.