I live in upstate New York,close to the boarder with Canada.I am starting to see fewer OBS trucks around,natural wear along with rust.Our problem area is the frames on these trucks,where the front,firewall forward,is welded to the c channel of the remaining frame.When I had my 95c1500 apart, I sand blasted the frame,then painted it with POR15.I was lucky as nothing was rusted through.If you ever had one of these completely apart,drive train,front clip,cab,and box,you might be surprised.It reminded me of the old trick that was used on 55 -59 trucks,that was to weld a sub frame from a Camaro to replace the strait axle and have a relatively new driving truck,along with the platform for your choice of engine.But back to the rust issue.I seem to recall that GM was promoting the use of 'hydro forming' the frames on these trucks.I wonder if this might play a part in why we see the rust problems that we have.The only other issue that might play a part would be the use of different qualities of steel,assembly plant to assembly plant.As I said,my truck has always been in the North East.The only real problem I had,was every line,brake and fuel,was rusted.As you know yourself from working on these ,or any vehicle from this part of the country,that is the price we pay for living here.I replaced all brake and fuel lines with stainless steel.I read somewhere,that every gear head should do at least one "body off" in their automotive life.It is usually a matter of time or money,or the reverse.My truck is 10 plus years in the making, and I stopped counting the money.