04 Chevy Silverado 4.3..Any known reason to be losing ground to individual systems on a at a time.

There is a ground that runs from the battery neg. down to the frame, and back up to the engine. But you need to fix any ground that is not connected, grounds can cause all kinds of problems.

Every known ground has been checked, cleaned, and repaired where needed...yet still took a jumper from pump and headlight to get them to work. Now ignition has lost ground but can't find where due to crank sensor and icm. using ground to signal firing order.

Have you looked on top of the motor for ground connections? I have one at the thermostat housing. Also it is important that the cab has a good ground connection, on my truck it is under the heater core inlet on the fire wall. You can't count on ground threw the cab mounts since it is an older vehicle. Otherwise, I can't tell you an exact location.