Well, it's cracked. How bad is it?

Opinions, everybody's got one. Mine, I would grab the broken wall section with needle nose vise grips and break it away. Then replace the broken tube and be done. The cast iron there is soooo oil saturated that no epoxy type substance will bond well.
The cast wall surrounding the tube never really needed to be more than 1/2 inch long. Consider the wall at trans tube entrance or any other example you can find. Even Briggs and Stratton LOL. The main difference is the interference fit design and lack of a tether/anchor like found on the tube of those examples. Basic engineering is "do it one way or the other".
If you can buy a tube for this application that includes external anchor, great. If not fab something. So long as the tube doesn't move enough over time to loosen in the shorter "fit" area, no problem.