GVWR was 6100-6250lbs (depending on equipment) for 1987
. The curb weight was in the 4400lb range and also changed depending on what the truck was originally equiped with. With the optional diesel engine, the curb weight was much closer to 5000lbs.
I have always found CK5's specs to be pretty spot on. My '74 is right at 3900lbs without a driver the way it sits.