Rear driveshaft length
 

88 K5 lifted about 6 inches. Looks like the yoke is out of the transfer case somewhat. Any suggestions on where to get a longer one in order to maintain parallel on the rear universal and the transfer case.

Be careful the angle of the U joints isnt too great. A 12 degree maximum if I recall correctly. Im told that lift kits used to kill driveshafts in the old trucks such that the shafts became hard to find used.

I'd measure the angle and look in a U joint manufacturers literature like Spicer to see what their max angle is.