I don't know why you guys risk it... I had a completely new rear d-shaft made w/ 1350 ears at both ends for my truck (which has 8" of lift) and it was less than $100 at the local d-shaft shop...
Just get a new shaft.
place in town wants to charge me 120 for a shorten and balance.

a new cv shaft costs starts at $495 front stock is $289
"1350 ROCKCRUSHER-1350 SLIP YOKE CV Conversion Shaft available for Blazer and Pickups This puts a CV assy. on to the rear of a special designed T-Case slip yoke for lifted or higher angle applications. See Illustration CV–6. Price is $495.00 for 3.00 tube and $525 for 3.5 tube for longer length applications. Call for additional Information."
http://www.thrashdriveshaft.com/4_wd_shafts.htm#GM PRODUCTS: CHEVROLET AND GMC
Most OE shafts are built with the slip assy closed more than we typically need.