The edge of the firewall on the cab needed patching. As I did decide to go with “quick & dirty” repairs to the cab, I decided to cut this flange off and just weld a piece of metal across the gap.
So the rusted mess was cut free, the paint & surface rust were ground back, and a piece of steel was bent into an L and welded across the gap.
This is where I ended up. In addition to being easier, this removes the lip that was trapping mud & water and encouraging rust. The lip is still in place above where the fender sits, so it’ll look normal under the hood once it is re-assembled.
It turned out to be a right pain in the ass to weld the lower parts of this. The weld kept trying to drip off the metal rather than stick in place, and I couldn’t find a good technique to avoid that. So a lot of swearing later I slowly manage to tack it all together.
Once the welding was done and ground down, it was painted with the same tractor paint as the rest of the firewall.
Then the whole firewall got a coat of truck bedliner, which, in addition to being very tough, did a great job of hiding the runs & other issues from painting the firewall.