Jerry is 100% correct about the modified senders. I'll post the junk I've found again in case anyone is interested. The sender won't work worth anything when this is done. I bought this unit from a popular vendor of AD truck parts. Since the seller didn't make the unit I won't tell you who it was.
Here is in my opinion the best gas sender I've yet seen:
https://tinyurl.com/y4htzvewIt is $28 with free shipping, it operates with a flat wiper and imbedded resistance wire and it reads right on the dot. Plus the thing is made of nylon. 30 ohms is correct and 0 ohms at the other end of travel is correct.
