[Schurkey]

PIck a gasket. It's not that critical. I've used many different kinds, and all the "name brands" work fine. Heck, my employer used to buy 25-packs of bulk gaskets, and even they worked OK. As said, the pan needs to be flat at the bolt holes except that old-time pans often had a sealing ridge embossed into the metal between the bolt holes.

Install the gasket CLEAN and DRY. NO gasket sealer.

Originally Posted by 69camarox

check the linkage seal it leaks down onto the edge of the pan gasket and runs around the gasket making it look like a pan leak when it is not

Yup, gravity and wind will move the ATF all around. Lots of "pan gasket leaks" have nothing to do with the pan gasket.

I've fixed a bunch of "pan gasket leaks" by
re-sealing the manual shaft, (any trans, but TH350 seem to be the most popular)
re-sealing the modulator valve,
re-sealing the torque converter, (verify the position of the converter bushing in the pump--Fords were especially bad at having the bushing shift which blocks the drainback hole.)
re-sealing the dipstick tube (after replacing the tube because it's cracked at the O-ring groove.)
re-sealing the speedo drive gear and/or housing (sometimes have to replace the driven gear due to groove worn in the plastic by the seal.)

Other sources are the kickdown cable/TV cable on a TH350 or TH700, and the O-ring around the electrical connector on a TH400.