Where are you from? Even here in western S.D. where rust isn't much of a problem, it is near impossible to find a 57-60 cab that doesn't have issues in the floor/footwell area. I can replace that stuff too but just don't want the whole extra labor to do it, been to that movie once when I picked a scab on a 72 and ended up halfway to the windshield to find solid melat. It didn't even have pinholes yet, just a few bubbles in the paint.
On a 57-60 you can tell before you even get up to the truck if the door gap is opening up at the bottom then it is probably rusted out in the cabmount