GMtuners (Sinister Performance) pinout chart for your swap is located HERE
They also offer parts you will need for the harness conversion, and reprogramming services for the swapped ECM. Get the service number from the white label on the ECM, and look for it on the list at the link above. There are many charts at the above link, so if your ECM is not on the first list, look around on their site, or contact them directly.
Pull and save as much of the harness as possible, and keep all connectors, relays, fuses, and switches if possible, and avoid cutting the harness if possible. Long wires are more useful than short ones when building a harness. Mark every connector with a label so you know what sensor, module, switch it came from.
1988 Pontiac Fiero Formula, Yellow, original. (CJB #118)
1977 Pontiac Le Mans Can-Am W72, original, unrestored.
1977 Pontiac Grand LeMans
2003 Pontiac Grand Prix GTP L67/MN7 (Parts Car)
2001 Pontiac Grand Prix GTP L67/MN7 (DD)
[This message has been edited by CJB118 (edited 06-11-2018).]