I had asked the same question awhile back on the other C10 board. The consensus was that most people only do it when they are installing air ride but there was a person or two on there that had done it:
http://c10forum.com/forum/showthread.php?t=9786
There is one guy on here who did a 2 inch Z on a 66(?) to gain ground clearance.
I had intending on doing the same but ultimately decided to bag my truck. If I was going to do it with a static set up I would probably do 1.5 inches as you wouldn't likely need to make transmission tunnel modification and it would bring your lower control arms parallel with your frame.