Here, the spotwelds are being drilled out around the perimeter of the cowl cover.

The left side of the cover is in much better shape than the right.

It was evident that the cowl was rotted out based on the condition of the floor pans. Looking up from under the dash you could see daylight. If the car was going to be saved, the cowl pans had to be replaced.
I started by drilling out the 150 or so spot welds in the cowl cover flange. I started out using a spotweld remover, but found the going too slow. After trying several different things I settled on a 1/4" bit followed by a 3/8" drill bit with the tip ground down. This worked much faster than the spotweld remover.

Next used was a combination of small chisel, steel scraper blade, and hammer to carefully pry apart the cover from the pan underneath. The cowl pans were so rotted at the ends that the firewall and cowl side panels were rotted as well. There wasn't much holding the front end of the car together. Note the attempted fiberglass resin repair by a PO. The resin was imbedded into the steel I was saving and had to be ground out prior to welding.

The right side cowl panel / firewall area was gone. The firewall had separated away from the cowl side panel as well as the cowl pan. If the jack stands under the front crossmember hadn't been there, the right side of the engine bay would have torn away from the firewall and dropped. Note the rotted section of the cover which had to be cut out and repaired.

The right side of the cowl cover. Note the damage to the cowl cover at the far left of the picture.

You can see where it has been separated at the firewall and left side.

The removed cowl cover lying on the garage floor

The right side of the cowl plan. The end of the pan is rotted away and the underlying firewall and side panel are rotted as well. Note the fiberglass resin which a PO tried as a fix.