The serial # is located on the block under the manifolds according to the previous chart. This explains the date and serial #s. Need to get the #, see if it’s after the date noted, May 1998. It should be if engines original to the Truck. The dates important because all blocks afterwards were pre drilled for oil squirters for wrist pin cooling. So whether you have them or their capped off, they can be added. Prior engines, only the PK was drilled.