[Jared at Pelican Parts]

That flexible piece is very prone to cracking. If it were me, I'd see if I could weld a small bead on there to stop the crack. If that is not possible, you might try using JB Weld, you just gotta clean that area good. (Someone once told me they developed that stuff to fix bullet holes in aircraft engine blocks during WW2.) That would be a temporary fix though.

The easiest solution might just be to bite the bullet and replace the section along with the catalytic converter. Pelican sells the repalcement part for Manual trannys at $354.25, for Auto Trannies, $486.00. You will also need new gaskets as well.