[hobgoblin351]

Yeah, U-joints with different size journals are difficult to find but not impossible. Most places don't stock them but they'll order them and in a day or two you're rolling.
I'd suggest going to a junk yard or a Pick-A-Part, and just buying a whole 9-inch rear. If you can find one from an 80's lincoln you'll even get the disc brakes! lol Measure the distance between the seats just to be sure it'll sit on your springs and then just bolt it in. As long as you're rolling you can beef it up in stages. Chances are the axles, unless they have surface rust on them are still usable. The all you need is posi, if you dont already have it and new bearings and gears.