When I bought my 72 I thought it needed a new exhaust system as I am 90% sure the one on the car is original. I had noted some surface rust at the time and assumed that is was rusted through. To use a football term "after further review" it appears that the exhaust system is solid, but just looks kind of discolored. My car is a low mileage example, (49,100+-) and my goal is to preserve all of the orginal stuff that remains on the car.







|UPDATED|11/30/2016 12:39:29 PM (AZT)|/UPDATED|

check out this link

Check out Jet Hot coating. It's good stuff and it really lowers the external temperature.

Well if you want to save it and use it you can have them removed and blasted clean. Then treat it with something like Eastwoods exhaust paint but it will look painted rather then bare metal. I used that on my new aftermarket exhaust 10 years ago and it still looks good.

|UPDATED|12/1/2016 7:28:55 AM (AZT)|/UPDATED|

If the car has been in Texas or the south all it's life it's probably original.  The killer for mufflers are short trips with the condensation never getting burned off inside and lying in the bottom of the muffler.   Up north rule #1 is don't run your motor in the winter when it is stored. 
My system is still original, the mufflers still sport the GM part numbers.  I cleaned the system from the cat. back 25 years ago with SOS pads and coated it with a clear spray coating from Eastwoods.  It yellowed a little early on but has maintained a nice patina to this day.  I removed the spare tire assembly at the time to clean it and provide better access to the mufflers.
 

The car was in California then Nevada all of its life. It was not driven in Winter and the mileage is correct.

|UPDATED|12/2/2016 2:21:13 PM (AZT)|/UPDATED|