1981 Chevy truck Wiring Diagram

[CrashOverKill]

Well my dually is having some major wiring issues. I have a short somewhere so started digging. I knew NONE of my gauges worked becouse when they did the diesel to 454 swap they just cut wires. I pulled the dash pad and to my horror there is wires cut everywhere under the dash and many of those twist on wire connectors. Ive managed to sort threw some of this and gotten the temp guage working. trying to figure out what color the oil pressure gauge wire is coming out of the bulk head connector to the fuse block in the engine bay.....hope that makes sense. Also the Tach. It has its own harness 3 wires 1 red with a fuse tap on it. One off white which looks like it went out to whatever on the diesel so Im guessing it goes to the dristributor and one black. Im guessing the black is ground but when I touch ground the tach goes straight to 5k LOL. Also found out this truck was once air conditioned they converted the under hood over but not under dash there is a bunch of stuff under there ive never even seen on a chevy truck LOL going to sorth that out while Ive got it torn apart. So any help here would be greatly appreciated