The easiest swap is 65 – 69 Lincoln spindles, rotors, calipers, master cylinder, etc. It’s the route I would go if I were converting your car.  The factory discs have big 4 piston Kelsey Hayes calipers and stops one of these cars with ease.  If you go that route get the 66 – 69 booster, master cylinder, and proportioning valve.  The 65 still used a single reservoir master cylinder.

GearHead Engineering offers a kit for $845 that includes everything.  abspowerbrake.com also offers a kit but the price is not listed on their website.  I have no experience with this kit but I’ve heard through the grapevine that it might not stop as well as using factory pieces since it uses a smaller floating caliper based off GM parts.

There are a few places offering large brake kits for these cars but as far as I know that all require at least 17 inch rims to clear the caliper and rotor.

If you go with the later model stock parts you’ll have to go with 15 inch wheels.