I purchased a new ignition tumbler and replaced it in the column. I grounded the positive side of the battery to clear the ECM memory. Reconnected both battery terminals and tried to start the car. The correct way to clear the ECM on your model car is to disconnect the negative battery cable and after 30 seconds, re-attach. This can be verified by replacing the ECM with a known good unit.
Engine check light comes on.
Engine runs so rough cannot drive. Original problem occurred driving 60 mph on freeway, engine light came on, lost power but made it 10 miles home. Has been to a local shop and to a Chevy dealer. The truck has a remanufactured long block with about 5,000 miles on it. New fuel and water pumps were installed at engine replacement.