The GSI should have the Delco EST distributor and TBI. Drop the distributor close to where it should be. Crank the motor over and adjust the distributor as needed to get it running. Get the motor warmed up
Once warm, shut the motor down. Connect a jumper wire or paper clip across pins A and B on the DLC connector, and connect timing light to No 1 plug wire.
Start motor back up and increase RPM to 1200 unless the engines computer has already don so. Now set timing to 10 BTDC. Once adjusted and distributor is clamped down, remove the jumper and idle motor down.