Just thought I would add a little something to this thread.
Was having problems with the fuel gauge on my M1009. I followed the steps in the manual to check to see what the problem was and it ended up coming back as the dash gauge being faulty. So I went and pulled the dash apart to get to the gauge and popped it out. Easy enough.
Here is the old one:
Then I went into my instrument cluster parts bin for a fuel gauge and ended up realizing that I didn't have a diesel gauge. I only had a gas gauge I pulled from a civi truck a while back. Looked pretty much the same except for the diesel one having "Unleaded Diesel Fuel Only" on it while the gasser one just had a fuel pump symbol on it. As well as the diesel one having some resistors on the back of the gauge. I thought that these resistors were needed due to something with the diesel pump in the tank. But after finding this thread, I saw the pictures posted by SouthernSteel of his gauge without the resistors on the back. So I said to heck with it and put the gasser gauge in to see if it would work.
Popped in the gasser gauge, turned the key and the gauge seemed to work and showed 1/2 full. But since the other gauge never worked and I didn't know if I actually had a 1/2 tank I went outside to the diesel pump and filled a 5 gallon gas container and then dumped it in the truck. Then I went back in the truck and turned the key and it went from 1/2 to almost 3/4. It works!
So it looks as if a standard gas gauge will work in the truck if that is all you have. I read somewhere else on the net that you absolutely need a diesel gauge for it to work, but it doesn't look like that is the case. I would prefer the gauge to have "Diesel" written on it, but this will do fine. At least I know how much fuel I actually have in the truck for once. At worst I can use my label maker to put a "Diesel Only" sticker on the gauge.
Hope that helps someone else.