I put disc brakes on the front of my 64 544 a couple of months back. I found a donor P1800 in a salvage yard in Kansas. Got the entire assemblies for both wheels for $100. I did move the shocks to the front of the A-arms (easy job), and there is a little interference when the wheels are turned to the lock. At first I adjusted the turn stops to eliminate contact, but that reduced the turning radius quite a bit, so I went back to the original setting--and don't bang the stops when I turn. I got the units off a 1967 1800, and the only real difficulty was getting them cleaned up and servicable after 30 years of non use. The bearings and spindles are the same, but the plate the calipers bolt to had to be re-drilled to fit the 544 spindle. I also had to move the brake hose brackets on the back of the backing plate to the front, and manufacture new hard lines so the original 544 hoses would work. I made no modifications to the master cylinder, or the original lines on the 544. Everything seems to work fine and the brakes are MUCH better. Also, the calipers are 3 piston and I ordered pads from the local auto store. Hope this helps.