I installed a 6" rough country lift on my 87 GMC 1/2 ton. after I completed the install I measured for front driveshaft length. I placed the bushings in between the frame and crossmemeber to lower the transfer case. With the sway bar in the vechicle I understand that there probably wont be much suspension travel. I jacked the truck up so I was able to let the springs extend, they didnt move much. I measured that I only needed about 1 1/2" more length. Does this sound accurate? I figured I would need more then that.

Just so this is clear....

" I jacked the truck up so I was able to let the springs extend, they didnt move much. I measured that I only needed about 1 1/2" more length. Does this sound accurate? "

What didn't move much? the springs or the slip yoke?

1 1/2"s, is this refering to what you might need to add to the drive shafts?

yes the springs, and yes the 1 1/2" is what looks like is needed to be added to the shaft

I would think it would probably be accurate (you could always check with a drive shaft shop to see what they think). Did you notice any of the normal discoloration marks on the slip yoke at the end of the drive shaft? That would give you and idea of where the end stabbed into the tail housing of the transfer case, and you could compair that to what is showing now. I know when I lifted my 84 K-5 4"'s I too put a 1" drop down on the crossmember. I also remember that it was easy to see where the slip yoke had been (depth wise) in the tail housing. Mine was pretty minimal, so I never did extend the shaft, although I had plans about maybe doing it someday. I never had any problems with it when I was wheeling though. Hope this helps.