Are you using the stock lever? Not the one under the dash but the one under the transmission? When I used the stock setup, the under dash lever moved about 80% of its travel before the brakes engaged. It held the car very well. Did you adjust the cable too tight? One tip is to press the brake pedal as you pull the lever. This 'pre-loads' the brake shoes closed and then you just add tension to keep the pads against the drum.
Your drums are self adjusting. That toothed wheel inside the drum turns to keep the shoes close to the drum.