Got a problem, need help/ gas leak

I recently got a new gas tank and sending unit and i installed it with out any problems. I unfortunately later broke off the end where the wire goes for the fuel guage. I had to take out the unit again to repair. Thats all done and seems fine. My problem is while i had the tank out again before i put it back in i tipped it to see if it would leak,,,,,,,,,,,,,,Well it did,bad. Not from the repair but the dam seal. I tried and tried but cant get the thing to stop leaking.........All parts are new. Totally stumped. Any Ideas????????