Rallye dash conversion

I've never done it, but yes they can. You have to carefully open up the fuel gauge. The VR is inside it and MAY be able to be repaired. OR you buy an external vr that you can "hardwire" so to speak to the back of circuit board.
I believe RT-eng. makes them.
@moparmat2000 and @RedFish are familiar with them.

But during my bench test I grounded the guage and it showed full, wouldn't this mean the guage is okay?