When you get the car, just go through the brake system and make sure everything is in good repair and adjusted properly. The drum brakes on these cars are actually pretty decent for the era from which they come. You can install a dual master cylinder (if not done already), and you may want to replace the booster: If its original, it is probably done or about to be done - same for the wheel cylinders. Also, get a brake shoe adjusting tool and adjust the shoes on all four wheels. If you don't drive like a maniac, the properly set up / repaired drum brakes should do fine until you get the scratch and the parts to do the disc conversion.