1991 Z28 5.0 TPI ignition timing

[71-LS6]

I helped my son with an engine rebuild for the aforementioned car. He dropped the engine back in and neglected to set the initial static timing on the distributor. I vaguely remember having to disconnect the distributor from the ECM in order to properly set the initial distributor timing. Does anybody remember what the proper procedure is for this car?
Thanks Steve