slippery stuff
Having spent 23 years in the transmission business, I can offer a little advice:
(1) Chrome is slippery. We would take a 3M Roloc disc and rough up the gasket surface so that the gasket would stay put.
(2) Don is right - if using a cork gasket, use some 3M weatherstripping adhesive to glue the gasket to the pan.
(2a) I know a lot of people have used silicone on gaskets, but silicone sealer works more like a lubricant - the gasket is more likely to squeeze out and leak with silicone on it than if it is installed dry, or glued to one surface.
(3) Check those pan bolt holes - if they appear to be pulled up (not flat) carefully flatten them out with a hammer.
(4) Again, Don is right - other leaks, like from the lever seal, or the filler pipe, will drip down onto the pan and appear to be the pan leaking. Also check the modulator and the servo cover. Best thing to do first is clean it off really well with solvent and compressed air, and observe the leak. You can use some cheap silver or gold spray paint temporarily on the potential leak points to help reveal the leak - the trans fluid will wash the paint off where it leaks out.
Good luck, as there really is not much charm in an old hot rod marking its territory!
440shorty