The key to the sheet metal welding is to fiddle around and find the right amps for the gauge and place you are going to weld. Get a good ground (I like the magnetic ground clamp) as close to where you are welding and listen for the light bacon frying sound. You need some copper heat sinks to back up...

Here are some pictures of the floor under the battery box.

I got a take off battery box last month for my M37. The old one was rusted through all around the bottom. I had to cut out portions of the floor under the box and weld in patches. I killed the rust with phosphoric acid and now it is primed and ready to go. I am in the process of striping, killing ru...