When I receive cut &/or flattened cans, I remove dents & holes best I can 1st. Then spot weld them to New or Donor cans when top &/or bottom rims have been cut off.
If can is cut @ seam to flatten & crimp of lids are still on I can usually mend w/ a small piece of tin spot welded to inside, then install new lids.

Spot Welded Flat Can to New can.jpg