63 Valiant disc brake swap kits?

How long has it been since the brakes were used? I'd pry back the dust boots on the wheel cylinders to see if there are any leaks starting. How close are the rivets to the edge of the friction material? I'd also pull the parts off, check all the hardware closely, lube the self adjuster parts, and replace anything that is pitted/rusty. Measure the drum diameter and if it's within specs, I'd reuse it as is. After you get it on the road, if you find a pulsation in the rear (pull the hand brake on slightly while driving to test), you can always pull the drums back off and machine them round again or replace them.