Ehaust studs and gaskets-replace?
 

Does one typically replace all of the exhaust studs and gaskets when re-installing/swapping the heat exchangers or do you use the old stuff? Typically I replace old hardware with new oem, but I'm not so sure about backing out all those studs.TIA

I wouldnt mess with the studs unless you have to. If you break some off you will not have fun. Gaskets should always be replaced.