.023 wire. Machine screw flat washers on some, but with that many holes to fill, why don't you just cut a new panel and weld it to the hump area? Gonna be a lot of work to make it flat.
Why would I want to make another one? Other than the extra holes there is nothing wrong with it.
What's wrong with it is all those holes! To each his own, but since there is nothing special about it ( flat piece of sheet metal, I wouldn't screw around with filling all those holes ( over 60???). You will end up with a better looking floor / firewall with a bunch less work. You already got the template.
