josh, i am not sure about the 68 beam, but this is what i have heard that
works.  take a splitty front beam and strip it.  then get some 71 trailing
arms with all of the disk brake stuff on it.  machine down the inner
bearing rid on the arms to fit the inner bearing on the early beam.
reasemble the beam and adapt the brakes as needed.  This is the quick
vertion.,  i have spoken a few folks who have done this with success.
hope this helped a little.

Take care and God Bless
matt