I rarely have issues with a pan gasket sealing well, and I just use the NAPA brand 727 gasket.
I believe most of the leaks are not really due to the pan gasket, but rather the selector shaft seal above it.
When that damn seal leaks, it looks like a pan gasket seal leaking.
I got a special tool on ebay to remove that pesky seal, but getting a new one back in while the trans is still in the car is a challenge,
and I have to resort to having a buddy tap it in from the engine compartment using a very long extension (using the installer part of the special tool package positioned on top of the seal) while I am below the car positioning the end of the extension to make sure the seal goes in evenly. I hate the job, but there is no other option really.
I used to think it was the pan gasket, and it was weird because when I would change the pan gasket, the leakage seemed to stop, but then if the car sat a couple days, it would start leaking again. I think this is because when the car sits a couple days the trans fluid leaks back out of the torque converter back into the pan and then when the level of fluid in the pan rises enough, it leaks out the selector shaft seal.
Because there is no collection area around the selector shaft seal, there is no pool of oil on the ledge above the pan where the selector shaft seal resides, so it leaks down around the pan gasket seal.
Been there too many times and know better now. Sometimes wisdom grows with age, but not always!
One tip is to not try to replace the throttle pressure lever seal when you do the selector shaft seal below it. Doing that in the car us a real drag since there is a very tiny e ring involved and you have to be very careful to not let the throttle shaft drop into the pan when you remove the e ring.
I have found that rarely does that seal leak probably because it is well above the selector shaft seal on the same vertical axis (hope you know what I mean - consult the service manual) so the fluid level never really gets that high.
If that throttle lever falls into the pan, then you pretty much have to pull the pan to get it back up correctly. I'll check later to see if I can find the special tool listing on ebay if anyone is interested.
Not that bad a job really when you have done it a couple times........................