I got the replacement firewall installed last night and put about 40 spotwelds on it. Seems very stable, I only welded the external flange thats under the gas tank for now. I may try welding the internal flange after the heater channels are replaced but I think I may need to move around the internal half of it a tad to match up with the heater channel replacements so left it loose for now.
The spotwelder is awesome for this kind of work since the steel on the replacement panel is so thin. If you get it clean its pretty much a no brainer to weld it right.
Clamp down flip the switch and zot.
Picture of the firewall looking down through the gas tank hole:
And a picture from inside the car, camera phone and dark rooms dont mix:
