2000 poniac grand prix gas guage

I would think the gas tank and gas gauge sensor is the same for both engines. The part is actually part of the fuel pump assembly which is inside the gas tank. That's not a repair I enjoy doing and a mechanic will want $200 and up, that's labor and fuel pump assembly and sensor. You might want to deduct that amount from the price you pay for the car. Being an older car, it's not a bad idea to have your mechanic pre-inspect it for you to see what else it needs. You can avoid a lot of headaches. I recall that V-6 can get leaky intake manifold gaskets.

Are you replacing the gauge sensor? If so it's in the fuel tank. Just sayin