I have a Ford C4 and have gone through the pain. Transmission pan gaskets - cork leaks!!! There are several different kinds of fiber gaskets plus at least one manufacturer that supplies a steel in rubber version Moroso 93102 - Moroso Transmission Pan Gaskets - Overview - SummitRacing.com
and not inexpensive, but they work. Those pan bolts - if they are conventional bolts and washers without an integral washer( flange head * ) - they leak. I'm using them as well as sealing washers** at 12 lb ft of torque. These DO NOT leak. Then there are Lokar dipsticks - the ones with a single 'O' ring can leak a lot. The 'improved' double 'O' ring version will leak less - Lokar uses the wrong diameter 'O' ring, at least for my C4. Lokar will either repair or replace that single ring dipstick for the price of postage one way - they sent me a new one. I'm now using a locking Hughes dipstick which has a GM type seal that does not leak.
* Flange head - McMaster-Carr
** Sealing washers - McMaster-Carr
As far as pans - all pans are not the same - I went through 3 new stamped steel, including a NOS Ford and now have a Trick Flow aluminum version where the bolt holes wont bend out of shape at normal torque tightness - here's one for the TH350 Trick Flow Specialties Automatic Transmission Pans - TH350 Transmission Type - Search Results for transmission pans - SummitRacing.com
Did the leak stop? No but it went from a pretty good sized puddle in 3-4 weeks to a couple of spots and my guess is that I have a minor seal leak.
Did I say that I went through the pain with the pans????
PS: If this fails, there are bigger problems with that transmission - seals, cracks (tailshaft with a TH350 seems to be not uncommon')