Intrument cluster pretty fubar, need help

[Deltantor]

Alright, so we bought a 4wd 1990 nissan pathfinder back in january, and have had a few issues with it that we have fixed, including a stuck lifter develop into a pretty bad metal on metal sound while driving it @ around 75mph, at which point we bought a 92 pathy with a stuck/bad manual tranny for -$100 (had some pretty awesome tires on it we managed to sell for $100 more than we bought the car for) and swapped the engines out. Had an oil leak after that, so we narrowed that down to a bad camshaft seal and during replacing that we realized we had a completely torn up spark plug cable so we put in new spark plugs and grabbed the cable off of the other (bad) engine and replaced it.

Which brings us down to the current issue, ever since we bought the vehicle the majority of the dash lights, the tachometer, fuel gauge, and water temp gauge is out. We pulled the dash out, and found a bunch of cut wires as well as a red wire with a wire nut just sitting loose back there. Was hoping it was just the dimmer switch so we bypassed that, and then had a pretty bad electric smell and the dash backlight came on pretty dim so we undid that. Wired up and put in a new voltage regulator hoping that might clear some of it up and it did nothing, even though the old VR was bad and the new one worked fine (bench tested them). The PRNDL lights do work, although they (and the clock backlight) turn off when you turn the headlights on. They do stay on though if the fuse for the brake lights is removed. The battery light is always on, same with the brake light which gets brighter if you engage the parking brakes. Did an ECU test, only thing it complained about was the oxygen sensor, replaced that with the one from the 92 pathy which fixed it. The turn signal lights work perfectly.

Does anybody have any idea what to do? I really wish I could get the fuel gauge working, and am really worried about the oil light not working as well, which might have been enough to save the old engine.

One more thing: Considering doing a rebuild on the bad VG30E engine in the next couple of months. Anyone have any information on that?