Put the swingarm on first, then install the drive shaft in thru the swingarm into the u-joint. Got to have some patience in lining it up. Leave the shocks disconnected when you do it so you can pivot the swingarm into the correct position. It took me about 15 minutes of putzing around to get it in there. I was able to almost see what I was doing with a spot light shining in the swingarm, laying on the floor, one eye closed and the other squinting :biglaugh:
If I remember right I let the arm hang down as low as possible till I got it lined up and started, then picked it up parallel with the floor to push it in the whole way. This thread has some helpful info on getting the driveshaft back in.
http://www.vmaxforum.net/showthread.php?t=8120&page=3&highlight=drive+shaft
Once you got the drive shaft in, lube the end of it and put the diff on with the bolts just finger tight. Put the axle in place to line everything up and then tighten the acorn nuts on the diff. Check out this pdf that has been posted up here on the site before on how to align the diff.