88 b2200 single cab short bed
no bumpstops
3 inch lowering blocks.
but still have 4 inches of wheel gap?
why?
Make sure the shocks aren't bottoming out. Remove the shocks and see if it goes lower. You also might have to pull a leaf or two out of the leaf springs.
What size tires does it have? If the overall wheel/tire diameter is small it could cause this. Your initial info doesn't say whether it is a 4x4 model. If it is then that might explain the problem.