Having removed the old battery and finding minimal damage underneath, today I cleaned up the sheet metal to neutralize any further corrosive material.
I used a toothbrush, a spray bottle, and some baking soda, which I’ve used in the past to clean up corroded battery terminals.
I scooped the baking soda into the spray bottle and then filled it with hot tap water. I shook the sprayer to mix it.
Then I sprayed down the battery tray area thoroughly.
The baking soda definitely reacted with some residual battery acid and bubbled pretty vigorously.
I went to work with my wife’s toothbrush scrubbing away at the reactive areas.
It was a mess so I put some shop towels down to protect the distributor and just repeated spraying to neutralize and wash away the mess and scrubbing to try to clean the metal.
Eventually I switched over to water in my sprayer to flush the area clean.
I made sure to clean off the inner fender area in addition to the battery tray area. The tray itself definitely has enough structural integrity to hold a battery and with the corrosion hopefully neutralized, the area should be stable from this point forward.
Although the inner fender was rusted through, the metal surrounding the hole is actually in pretty good condition. I may want to do some work to repair or at least tidy up this area of the engine bay, which wasn’t on my original list of jobs for the truck.
Here’s a shot of the red battery cable going down to the starter.
The black cable was grounded to the engine block. Since the black cable was connected to the positive terminal on the battery, it appears that this truck maintained the original positive-ground configuration that these early trucks had from the factory. More modern vehicles are all negative ground. My understanding from a limited amount of research is that you can easily convert a 320 to negative ground by reversing the cables and everything except maybe the radio (which was a rare optional item that my truck lacks) will function properly.