Rear discs do save weight, that was the big reason we switched on Tim's Valiant. The car didn't stop any better but it saved weight and the braking was a little more linear. Drum brakes are non-linear and you can get in trouble in a race car with drum brakes if you aren't careful. For a street car I think the drum brake is a better design since the parking brake is dead simple. But having said that, my street cars all have 4 wheel disc brakes so I don't follow that advice myself. I do sort of regret switching to disc brakes on the rear of my Coronet. That car had the big station wagon drum brakes on it and it stopped on a dime. The parking brake also worked fantastic. The parking brake I have now doesn't work very well and the brakes don't feel as solid as they did when the car was disc/drum.