Just do a thorough rebuild on them. Overhaul/replace wheel cylinders/master cylinder as necessary, replace the hoses, flush the lines (replace if in poor condition), and recondition the drums (If in spec, otherwise replace them). Properly adjusted, the drum brakes will be fine. If you can, look for shoes with an "FF" code. Those are the high friction shoes, will get you more stopping power. Other than adding a booster, there's not really much more than you can do with drums.
