Welcome to Allpar. Is the camshaft and distributor turning OK? Is spark the only missing ingredient?
Try this wiring diagram at Fig 62: http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c15280251c88
Make sure that you have the 12 volts at the Dk.Gn (or turns into Gy/Bk) out of the ASD relay to the ign coil with the engine cranking and battery 12 volts at the red wire to the ECM.
There should be either 5 or 8 volts to the various sensors and distributor pick up.
This is kind of a generic 1989 diagram, but the wire colors and ECM pinout should be pretty much the same. The Omni/Horizon is the AL-body.
Review all underhood wiring and connectors to make sure that nothing got unplugged or pinched during the head gasket change.