I just put a set of Rough Country nitro 9000 series on my 86. I'm not certain because I bought it this way, but from measurements I've taken of brackets and blocks, it's got about 4" in front and 4.5" in back. Only done a quick drive though the neighborhood to test it out. The previous shocks were absolutely shot. After taking one off, I compressed it and it didn't go back out on it's own. It makes it ride so much nicer. It's like a different truck.
The way I shopped for them was, I went to several large online retailer websites. Put my truck info in and it brought up shocks that would work. When you make your selection, there will likely be some sort of menu to choose from various lift heights.