Rust and Dusters

I've owned many Mopars pretty much all of my life. You know how you learn what cars typically rust where. I'm looking forward to buying a Duster and doing a Magnum Efi swap this year. I've got a couple of Darts and an E body. I know about where to look for the "typical" spots and what it usually means. I looked at a car locally today that was a Cali car. It was very rust free. The thing that concerned me was a couple of pinholes in the spare tire well and the lower quarter panel. I just find it strange the car is as rust free as I've seen but the trunk being hurt scares me that more is hiding. Not typical for a socal car. Is this common on dusters? 99% solid and a trunk rotting through?