I've seen 3-pin and 4-pin connectors on the '91-93 4L60s. Scott's pictures are helpful though; they look COMPLETELY different. If you can get the front of the car up on ramps or gently drive the front wheels up a curb, you can probably just slide right under the car and use a mirror and a flashlight to see what the plug looks like. It'll be on the passenger side, on the top of the valvebody area, towards the rear, facing upwards towards the body.
"The unexamined life is not worth living." - Socrates