Need Gas Guage Help

I have an 86 grand marquis, we recently put a new gas tank on and I was hoping that would also fix my failing gas guage problem, however it didnt. Does anyone know of anywhere I can find a gas guage and kit to put on the car? Also, the gas tank we put on is from an 89 Lincoln town car (it's bigger than the stock), would this make a difference?

when u changed the tank did u use the old sending in the new tank or did the tank u put in come complete with sending unit? if u used origanal sending unit that may be the problem.

There was a new sending unit in there but my brother said the plug didnt fit that led to the gas guage.