I got the bolt in lower firewall of the 37 out and I decided to weld up all the unused holes in them, the smaller holes can just be welded up but the larger ones need plugs welded in. Any suggestions on how to make some round plugs? The metal is 16 guage.

Also should I weld with my Miller 35 and .035 wire or my Miller 110 with .023 wire? I'm using argon/C02 mix for gas.

I've heard guys claim you can plug weld a 3/4" hole or larger with a copper backing spoon.

http://www.harborfreight.com/welding-spoon-66785.html

Find a steel electrical junction box and use the knock outs for the plugs and I use the .023 wire on everything.

.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.

Turn up the wire speed and burn the holes shut. You are lucky the panel is off the car it will be much easier!

Those are galvanized, don't breathe the fumes.

Shows how rust free the truck is, only broke 1 bolt off and I just drilled an tapped it back out to 1/4-20

Why would I want to make another one? Other than the extra holes there is nothing wrong with it.

Bu my count 27-28 unused unnessasary holes in the lower fire wall, most are 1/8-5//16, those will weld up easy

I stopped counting at 60 holes on my truck.

There is another 30 on the upper firewall, I will have to just use rubber plugs on those for now.

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.

All done with less than 2 hours labor, looks good

So now that the holes are welded in, what was your technique? Copper backing plate , metal filler pieces?

Yes, both those methods, copper backing plate for the small ones, fillers for the big ones