The A/C kit I have from North Racecars puts the evaporator behind the dash on the passenger side. Only there isn't enough room between the dash and the firewall to mount the evaporator. So you have to modify the firewall to accommodate. I knew this, so it is a complete mystery to me why I decided last December that I could go ahead and rivet the firewall in place. But there it was, and it needed to come out.
Most of the rivets were simple to drill out. A good drill goes through aluminum rivets like butter. But with the engine in place, a few were in tight spots, so tight that I couldn't even get my right-angle adapter on them. A chisel solved that problem. Knocking the head off an aluminum rivet with a chisel is almost as easy as drilling it out.
With the firewall out, I was able to cut it and bend it:
Then I made two triangular end pieces, using my brand new bending brake from Harbor Freight:
Then I fitted them into place, drilled for rivets, and installed with Clecos.
This was my first sheet metal fabrication, and I think it turned out great. It makes me look forward to some of the other fabrication I need to do. (Battery box, I-Squared controllers, maybe more.)