You might as well save yourself some time now and pull the driveline. You'll either have straps or U-bolts on the diff. Yank those, and do as the previous member said (slide the driveline to the rear) and it will simply slide loose.
I'd take some tape and wrap around the rear U-joint to keep the cups on. Otherwise they could fall off and the needle bearings could dislodge. Then you'd be forced to choose between trying to put them back in, or getting a new set of needle bearings/cups.
------------------
'69 3/4 ton C20 2wd w/ 350ci/400THM and a wood bed!
'69 3/4 ton Custom 20 2wd w/ ORIGINAL 350ci/4sp Manual and a wood bed (parts beast).
Seattle, WA.
*See pics of my trucks and project at
www.webshots.com!