Replacement body panels

I know this will sound odd,at least I hope it will,but I am looking at having to replace the cab corners on my 99 Silverado e/c and would like a reputable source to buy from(quality panels).I hope this is odd as I would hate to think that the new body style wont last any longer than a few years before rusting out,but I begining to think that my truck has at the very least seen alot of salt air from the coast if not salt water from being stuck on a beach.There seems to be alot of things showing up now that I find odd the least of which is the bubbling of the cab corners as well as the blister on the passenger door,I mean aren't these bodies supposed to last for years,being galvanized and all?

I know this will sound odd,at least I hope it will,but I am looking at having to replace the cab corners on my 99 Silverado e/c and would like a reputable source to buy from(quality panels).I hope this is odd as I would hate to think that the new body style wont last any longer than a few years before rusting out,but I begining to think that my truck has at the very least seen alot of salt air from the coast if not salt water from being stuck on a beach.There seems to be alot of things showing up now that I find odd the least of which is the bubbling of the cab corners as well as the blister on the passenger door,I mean aren't these bodies supposed to last for years,being galvanized and all?
GM parts has these I am sure, for aftermarket try, Keystone Automotive, nationwide company, and B&D Int'l.