I agree that's why I pasted the link, seems as thou Dodge electrics are a bit quirky. The fuel gauge is one of the most talked about from some of the searching I did.

Maybe take a ride back down to that junk yard you found and look around for some early 70 dodges. The fuel gauge and senders are more then likely electrically the same. If you find a sender and the ohm measurement is in range 240 empty ohm, 33 full ohm, move it to the sender you have. If the tank fitting is the same and the float arm to short/long a little cut and past will do it.