Hmmm, if your truck is a 1987 B2000 and it still has the original engine, your rocker arms can be adjusted and therefore quiet down your valve train noise.
All of the B2000 trucks came with a 2.0 engine and they had mechanical rocker arms.......now, if your head has been changed and an original 2.2 head installed then it is possible that the installer left the hydraulic rockers on it and you have the typical hydraulic lash adjuster (HLA's) bleed down problems. You can remover the valve cover and tell (might even be able to look through the oil add hole) just by looking at the rockers.
Hydraulic rocker arms do not have the adjuster nut on the top of them.....like so.....
Mechanical rocker arms do.....like so....
Closer pic of the mech. type.
Here I was swapping out some hyd. rockers for the mech. ones........you may need to click on the pic to zoom in on it and see it better.