Ok, I have a problem that is a pain.
Car's gas guage and oil pressure guage not working. Sometimes they work but most of the time not. I have changes the pressure sending unit and checked all the fuses. Other than that I have looked at some wiring but figured I would ask here first. Battery works as well does the temp.

 

I've got the same problem, haven't found the oil pressure issue yet, but found my fuel sender was very rusty, in fact mine has rusted apart so I need to replace it, the sender is on the upper side of the fuel tank on the drivers side, easily accessible through the wheel well, remove the plug and clean it very well.

 

I know that the condensor that is bolted to the rear of the engine has something to do with your oil pressure gauge as I didn't reinstall mine after a rebuild and tried to figure it out and the manual shows the condensor hooked to one of the oil pressure lines, when I hooked it up it started working again, before it would just bury itself.

 

Check, I just read that about an hour ago when I was looking in the factory service manual for the 85.
I will see if the condensor is there.