How do you change the valve lifters and set the tappets on a 1991 gmc 305 cid engine?

To change the valve lifters on a 1991 GMC 305 CID engine, first, remove the intake manifold and valve covers to access the lifters. Take off the pushrods and rocker arms, then carefully extract the old lifters using a magnet or lifter tool. To set the tappets, rotate the engine to the appropriate position for each cylinder, adjust the rocker arm nuts to achieve the correct clearance (typically 0.006 to 0.008 inches for hydraulic lifters), and reassemble the components in reverse order. Always consult a service manual for specific torque specifications and procedures.