My hybrid '76 has stock brakes all the way around. For most street driving they really seem to be sufficient. I haven't had any situations where my brakes faded and scared the out of me. Although, I haven't tried to autocross this car and I really don't know if the stock setup will handle that type of abuse.
I am building a Velo Rossa on my '71 chassis and am planning on extensively autocrossing that car. I purchased a 5 lug, rear disk setup from Mike Gibson at Future Mobile. I don't have the car on the road yet so, I can't really say how much better they are.
There is an avid and very knowlegable autocrosser that posts frequently at HybridZ that feels the rear drum setup is quite adequate even for hard track use.
By the way, here is a link to Ross Corrigan's site: Modern Motorsports