[dsraven]

yeah I know, school from the seventies with that narrator guy. haha. anyway, it's good to understand how it works before you spend money and time.
you will need to remove the rag joint from the column shaft, clean the shaft, measure the shaft where the splines are, count the splines and then look for a u joint to fit that shaft size and spline count with a DD shaft connection on the other side of the u joint. that is assuming you will use a DD shaft to connect your parts. from there you will need to find the same info for your steering rack input, shaft size and spline count, and get a u joint to fit that with the same DD fitting on the other side of that joint as the DD shafting you will use. some of the problem with the rebuilt racks is that they could be mustang II or thunderbird and the splines may change over the different years. always good to confirm. as well, I think they were different from power steering to manual steering so that throws another confusing issue in. that's why it's best to do a hands on count before you get knee deep in gators.
then attach the u joints to the column and to the steering rack, once the column is mounted of course, and then try connecting the dots with a piece of broom handle or something similar. if it is obvious that there is no way it will connect, like something is in the way for a straight shot, then install a shorter broom handle into each u joint and bring the parts together. ensure to bring the parts together in such a way as to leave room for a support bearing on the upper end of the connecting shaft if required. this is where having the engine merely mocked up can help you out because you can jack the engine up or down as required to make space for the shaft to clear. you will need to do some angle finding to try and get the angles of the shafts to match so the u joints have the best chance of not binding. try to get it done with a single shaft or just 2 shafts if possible. otherwise it becomes a nightmare of trying to match angles and support the intermediate shaft so it doesn't wiggle around and cause binding.
I don't personally recommend a rag joint unless the shaft is a straight shot (angles match) from the column to the next shaft in line. they are only made for a directly straight on connection or very minor angle difference.
it would be best to match the angle of the column shaft with the angle of the steering rack input shaft, those angles will cancel each other out that way. you can accomplish that by rotating the rack with a wedged style mounting bracket shim until you get it right, then either tack weld the shims in place or rework the mount to match the new angle. just ensure that the tie rods stay true to their original plane, inline with the steering knuckle connections, or the geometry will be out of whack causing steering issues.