If there is one thing I have learnt over time it is how different rust developes in different areas of north america. Then there is a kind of subdivision of the type of rust followed by how localised it is.

I have seen nice cars with rust issues confined exclusivley to only one area but advanced there. As well as cars with rust all over the place but not too advanced.

You have to get the car up on a hoist and check it to really tell. If you were extremely lucky that rear shock was frozen by the five years sitting and just punched through the lower mount. Rust need not be a large factor for something like that. So the first check is to see if the shock is frozen.