Odd place to rust

[Livrat]

At first sight my thoughts were what an odd place to find rust in a truck around here.. then upon purchasing the truck and removing the rear window.. (with hardly a push) out fell about pound of soggy rotten peanuts.. looks like some type of rodent had been using this area as cafeteria and latrine.. Big Bummer!!
It was a real shame as the whole bottom of the truck was rust free!! And to boot it was a 68 Big block 50th.. Oh well.. Another donor...
Anyone ever seen one rusted out here before??