Heaterbox Pipe Passthrough - Reinforce vs Remold

Hopefully the title makes sense, but here's a description and picture.

The area of my heater box where the pipes for the heater core pass through is broken. I was able to push the piece back into place, but I am trying to decide whether I should reinforce the cracks with JB-Weld Putty or cut the lower section out and rebuild it out of putty completely instead.
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