Power back tailgate glass problem

[68ss]

I have a question that I'm needing help with. I've got a 1984 gmc suburban that has a sliding back glass. The guy I got it from rolled the back glass down then pulled motor and trans and sold it. But before he sold it he cut all the wires that go to the plug that plugs into the side of the steering column and a few other wires. The back window switch is gone and I'm not sure what plug in plugged into the switch. We've tried everything to get it rolled up and we've had no luck. We even tried to go to the wire in the tailgate that went to the motor and put the hot wire to a battery and ground the ground wire to make it go up like that but still nothing. If anybody can help me with this or has any suggestions let me know. It'll all be appreciated. Thanks