I am sure this can be repaired if you take it out and take it to a
radiator shop. I believe the end tank will have to be removed. With
all that in order and cost, I probably would just get a replacement
radiator to drop in.
If you used Genuine GM oil cooler replacement lines, you will most
probably be doing that repair again. Genuine GM lines are garbage.
They WILL leak at the crimps sooner than you would expect. My company
takes the complete old line sets to a hydraulic shop now. They reuse
the ends and attach stainless steel braided lines to them. Never have
to mess with them again!
Good Luck, James