I see oil pans on ebay pretty often. No sense patching on a piece of Swiss cheese! A good welder can probably replace the entire bottom of the corroded area with a piece of NON-GALVANIZED sheet metal, about 16 or 18 gauge. Galvanized metal gives off toxic fumes when it's welded, and the zinc coating might flake off and score bearings.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!