Replacing single reservoir M/C with dual reservoir on four wheel drum system

It is hard, since you just bought 13 in tires. In todays world I would buy 15"x 6" Ralleye wheels, Wheel Vintiques 61-565404 Wheel Vintiques 61 Series Chrysler Rallye Silver Wheels | Summit Racing and get a set of original Kelsey Hayes disk brakes or 10 in drum brakes. The 9" brakes are weak and I would not put any money into them. You can easily convert to a dual master cylinder, all you need are new front brake lines and a 67 A-Body up splitter. What are your long term goals for your wagon?