I'd get the pan off. I bet your interference is the front diff?

Crawl under and look how you can take loose a couple of big diff carrier bolts and the diff swings down enough to let the pan just clear. Watch your head...

Not much chance of getting good beads of gasket goo on the pan flange or truing up the flange if you can't get it off.

To true the flange, feel the pan bolt holes on the engine block side of the flange. Feel the slight dimple from the bolt clamping? This takes two people, unless you can hold the pan in place with knees or feet or elbows or other appendiges. I put the fattest socket that will fit in the bolt channel on the pan flange against the outer side of the hole, in the channel. with this socket and a long enough extension, put the pan flange block side up, set the other end of the extension against a dead stop (anvil, etc), and using the rounded end of another juck 3/8" extension as a punch, knock out that dimple until it's a shallow volcano aimed away from the block. This greatly flattens the whole flange area and really cuts down the gap gasket and sealer have to fill, and increases gakset clamping force.

My new rule #28 of life. Make every effort to seal it up....