89 Cav - electrical problems

I've been working on this 89 cav for about a year. Dropped a rebuilt in it and got it running - runs good. I have several problems that seem to be electrical in nature....

1) the oil pressure guage shows no pressure. I replaced the oil pressure sender and checked to see that the bypass port in the filter mount was free and not clogged. Every time I start the thing, I take the filter off and its full of oil, so I believe the new oil pump is pumping away.

2) the temperature guage shows red hot - its all the way over. I replaced the temperature sensor and tested it - the resistance seemed to be good (4500 ohms and its about 55 degrees outside).

3) the tachometer shows about 500 rpm while cranking the engine to start it. Once it starts, the tach goes way past the stop at the high end. Since I can hear the engine idling, I know its wrong.

4) when I turn on the headlights, the dash panel lights come on, but all the gauges (temp, oil, fuel, tach) all go out.

5) the outside thermometer shows that its 160 degrees outside. That's obviously wrong.

I've been over and over all the electrical connections - this sounds like a ground problem to me. I took the two sets of ground wires off the transfer case connections and cleaned them up and tested them - that's not the problem.

I tested all the fusable links that are attached to the started connection. All good.

I checked all the fuses - all good.

I have one green wire coming from the firewall that I can't find a place to plug it in. I've connected the crank sensor, knock sensor and O2 sensor and can't find any empty plugs.

I've checked under the dash to see if vermin got into the wiring - nothing obvious.

I'm at a loss. Anything you guys can suggest would help out.

To make it easier I would run a seperate ground from the battery to the dash. This will require drilling a new hole in the firewall but it can save a lot of "Gremlin chasin". Good Luck.