I was lucky when I bought my 40 project, it came with several extra gauge clusters, so I was able to come up with good working gauges. But it's pretty easy to check and test your gauges. The amp gauge doesn't care if it's 12 volt or 6 volt. It just measures current. If you measure across it with an ohm meter, it should measure close to zero ohms. If not, then it has a problem. If yes, it doesn't necessarily mean it's good, but it indicates that it probably is. You'll have to feed a larger amount of current through it to be sure. The gas gauge DOES care about 12 volts. You'll need to buy a voltage reducer for it, unless you can find a dealer who offers a 12 volt version. I've found that the active reducers sold by the dealers work fine. I can't remember if you need a different sending unit for 12 volts or not, but I think it probably does. The temp gauge, and oil pressure gauge are strictly mechanical and don't care about 6 volt or 12 volt. You can put the bulb at the end of the temp gauge tube in water that is boiling or near boiling to see if it works. Connect the oil pressure tubing up to a running engine to see if it registers. On the 1940 trucks, all of the graphics are printed on the inside of the large rectangular glass. I tried to wash mine, and it washed the printing off, so I had to buy a new printed glass. You can send the chrome outer trim off to be re-chromed. I painted the background of the cluster with old fashioned ruddy red primer. It isn't an exact match, but is in the ballpark, and it looks good with the other interior colors.
