[68gtoMN]

Here's my take...
The metal dash is what the radio mounts to for a solid fitment and the lock nuts on the radio shafts tighten against the opening. There is a rear brace that attaches to radio then dash to hold weight of rear of radio also.

Were it me, I'd find a way to repair that opening before installing the bezel and any original radio. You might be able to locate an original radio dash section, then cut/weld to return to original. Just thoughts. Not knowing your timeline and desired effort/end results, I can but opine.

good luck!