The Granada spindles lower the car IIRC. I think most of the Thunderbird suppliers sell kits, pretty much like I installed 20 years ago. There's a spacer that goes on the splindle and allows a different bearing, a Granda rotor with the center turned down for the early wheels, and a custom bracket to mount the caliper. Mine came with an Fairlane caliper, year unknown. It moves the wheel out about 1/8", which isn't normally a problem. I used the oem remote booster, and the kit came with various other bits and pieces. A new disc/drum master was included, and the boost was only used on the front disc. I don't recall if different rear brake cylinders were in my kit (for brake balance), but some do.
Proper adjustment of the rear drums was critical. Brakes were good with the stock tires, but when I went to wider tires I couldn't lock the fronts until well after the backs locked up. Turned out to be the pads were too hard. With the right pads, proportioning valve etc. it all sorted out.
An acquaintance who lives close enough to go down looked at the front disc set up at Prestige Thunderbird. He's got a 56 pass car, and was really impressed by the engineering they'd done to solve all that, and they apparently do that for the full size car. I think that would be worth a phone call to them.
http://prestigethunderbird.com/