If the previous guy tightened the pan bolts "farmer tight" (as tight as they will go, then another half-turn) and overcompressed the pan gasket, you may have enough ripple and distortion to the bolt flange on the pan that getting a seal will be a problem. A flat flange seals up nicely with just a fresh gasket and PermaTex High Tak, but if there is a ripple in the pan, you may need something more flexible to conform to the waves and ripples.

Good luck