just run it!
Its not too costly to have it professionally welded..thats the best solution..
I've run more than 1 tranny with an ear broken off,and never had any trouble!--not that I reccomend it--but I had driven one truck for 5 years before I noticed one bolt ear was cracked away from the bellhousing during an oil and filter change...I never bothered to try to do anything with it--I eventually sold the truck..the tranny never gave the next owner any grief either...he did clean the cracked area and smeared J-B Weld on it,but I doubt that did anything but make him feel better about it!
I even ran a buick TH350 tranny in a 67 Caprice I had--I bought it cheap with no tranny and a lower ball joint was snapped after someone slid into a curb on an icy road..the guy said it came with a "new" tranny in the trunk--after I got it under the car I realized it was not the chevy bellhousing!

--my brother said it would still fit and work,but only the 4 lower bolts will line up!...he suggested getting an adapter plate,but by this point I was already disgusted with the car,so I threw the tranny in anyway,using only the 4 bolts.
..I started up the car,and filled the tranny up with fliud,and went for a ride--it was a pretty nice car otherwise,so I kept it,and planned to swap another Powerglide or chevy TH350 into it someday--but I drove it 15,000 miles that way,and it never gave me bit of trouble!--of course I did not do any brakestands or hole shots (only had a 283 2 bbl anyhow!)...a few years later I sold it to a friend,he never changed the tranny either,and did not plan to unless it gave trouble...we just locktighted the 4 bolts,and made sure they were tight at every oil change..

however,I dont think this would last long in a 4x4 application!..