http://www.ebay.com/itm/1989-Chevrol...b7f563&vxp=mtr

I have one of these for my 1988 and it will answer all your questions about your entire electrical system. I built my entire harness (excluding basic functions on left side of firewall) from a GTO harness and when anyone asks how I did it, the answer is always the same," One circuit at a time".

88-91 does NOT have DRAC, they have a similar module IN the cluster. The cluster NEEDS to see a 40 pulse per driveshaft revolution AC signal, that's why the VSS sensor ring has 40 teeth in an automatic transmission. Be glad you don't have to deal with A T56 and 17 tooth VSS.