K-rich711

Hi all I'm looking at potentially buying a 350z as a second car. I've had a look at the buyers guide and done some research online and from what I can find mechanically they are pretty good, oil gallery gaskets seem like something to look out for on the HR but generally solid. Noticed several reports of bottom end knock although I'm wondering if this is due to a ignored failed gallery gasket rather than a weekness in the engine? What I'm more interested in is any areas I should check for rust? I've seen a few in person with rust around rear arch's but not sure how common of a issue this is? I seen talk of rotten W braces and a kidney brace? But I think these are bolt on parts so sound easier to deal with. Also are all cars the same rust wise? Are the later models any more resistant (maybe a change in design etc) other than just being newer. Cheers for the help