1969 4x4,
I put a 6" lift on my 85 Suburban and belive it or not I didn't have to change the drive shafts out. It was my daily driver so I didn't really notice any problems until hunting season came around (almost a year later). When I did alot of off roading I realized I was maxing them out with the articulation.
I had a rear shaft made for around $200 and the front was a little cheaper.
I would suggest replacing them as you are doing the lift but worse case you should be able to drive with the stock shafts with it lifted.
This was my 2-cents
................Hope it helped!
