Fuel gauge dosnt work after wireing harness swap and motor swap

Hey guys , i have a 2000 grand prix gt and i put a 97 gtp engine into it. I had to swap out the harness as the 1997 isent interchangable with the other years.. Short story short , i only swapped the harness under the hood and the one in the dash. I dint swap the one that connects to the passrnger kick panel and that runs out back because they seemed fine to me and clicked in togethor.. Well my fuel gauge is like passed the full limit... Would i need to swap the rear harness as well ? And my trunk randomly opens and it wont open wen i press the button.. Advice would be very apreciated... Thanks

I would sell the 97 motor and get a 98-03 motor so you don't have this issue.

Well its already in the car... It was a big job to do it tooo:/

BUMP.., k write down. its not the sending unit , the harneses are fine togethor, fuel gauge goes over full when key is on, anyone with any ideas? about to go to a mechanic if i cant get it and i want to save my money....