1990 Chevy 1500 trans swap

He guys, I hae been trying to find a diagram to help me find the reverse wire / signal wire for a friends truck. The truck is a 1990 C1500, 4.3L. It was a manual and someone put in a 700r4 or a turbo 350 (can not find any identifiers). I have found the pig tail for the reverse indicator in the factory harness, almost in perfect alignment is the pigtail for the Auto trans. The Auto trans has 3 wires, I have identified the 12v and connected it to the correct harness wire (someone had run a jumper wire to it from the fuse cluster. I have tried to ring out the other 2 wires in the pig tail with no positve answers. I went to the column - at the base there is the Nuetral safety switch, I questioned if it was in there - no luck. The sterring column was replaced with a auto one. Does anyone know where I need to check into next? I can post pictures of the situation if needed. Thanks as always, Brian. Well I answered my own question......the neutral safety switch had a cover block over the reverse terminals. When I removed the block - I found the two bladed ends, I ran a green wire to the reverse signal wire by the transmission, and found the correct power feed under the dash and hooked it up - works great! I feel kind of stupid for not figuring it out sooner, but I posted this reply should anyone else have a similar issue.Car Repair Talk's forum.