There are a few different types of body drop. I'll try to explain the most common as best as I can. A body drop will lower the body of the truck in relation to the frame. On a first gen. its common for a 3.5". This is accomplished by cutting around the inside of the body in the cab, separating the floor from the sides of the cab. The body is suported somehow, probably jacks too keep the body from slamming on the floor when all cut out. The interior must be stripped. Once the floor is cut all around, the cab is then lowered down, covering the frame. The floor is then rewelded to the cab, all along the cuts. Kinda difficult around the firewall/tranny doghouse. The front bumper mounts are cut and lowered too, or the radiator support is cut down. This looks like your truck is lowered 3.5(or whatever the amount of drop) without any suspension lowering. Usually done to get the body down more when a truck is laying the the frame. It does not harshen the ride any. It will lower our truck without any ride difference. This will cause clearance problems is its already lowered. You will loose head room, whatever the amount of BD is.
Now, usually most guys do this with an adjustable suspension, air bags,hydos, etc, to lay out the body. I was thinking of this with just a small static drop, like 3-3". Then maybe a 3.5 body drop, and it would look like a 6.5" drop, and ride like almost stock. My problem is that I've got headers that wrap around the steering shaft for my v8, and the shaft would hit the headers when it was done. Its not for novices to do at home. Most shops charge around $2500 for a body drop. A suv(like our blazers) is harder than a truck. Because you can't do the cab and the bed separate. Anyways, I hope this helps. Any more questions just ask, I'll try to explain the best I can