Nope, wet sand and go pound it.
That is actually how the Brits made headers for the GT40's in the 1960s - all hand bent. They would take dry - really dry - sand, pack it into the tubing, weld it shut, then heat it in a furnace and hand bend it around mandrels to shape, each tube one at a time, then clean them up and weld them at the collector. They were cut equal length and had to match up. Packing them with sand would force the tubing to stay round and not collapse or wrinkle, unlike air bent at the muffler shop.
Fill the scabbard with sand and then add pressure, the dents will finally move out. Bondo won't work, it eventually falls out and you haven't done a thing to fix the actual problem.
There is also the concept that collector value will be determined by the method used - sand is restorative, Bondo is hillbilly. Refinishing or polishing it may reduce it's value, too.
It's 144 years old -