Question about t-5 bell housing

Drill it out and install a Heli-Coil if the pice that is broken of is where the threads are. You can get one at most parts stores. If the portion that is cracked is on the outside then I'd probably just smooth it out with a dremel or a file or something and make sure that it's not cracked through to the bolt hole. Then ride on with the thing. Check it when you're under the car for oil changes etc. just to make sure that everything is staying put.