I have seen this done, there are a couple of kits on the market to do this. If you want to do it yourself make sure that the rack you get is a rear steer unit and is approximetly the same width as your 55. Try maybe a fwd mini van. check the length of the steering arms from the center of the spindle to the hookup point for the tie rod end and try to get this as close as possible. I have read about people using a ford tauras rack on early mustangs and increasing the turning radius by as much as five feet. Sounds to me as if you are a do it yourself kind of guy, so get out the measuring tape and head for the salvage yard. I went with the 605 box conversion on my 57 210 and am very happy with itwith one minor exception. the rear most plug on the left side I now have to change from underneath the car. As far as the disk brakes, I would buy a complete kit as by the time you buy just the brackets and then get everything else local you will have spent just as much as if you bought the kit in the first place, I know I did it that way on my 57.