Jordan,
The asbestos covers seem to have been specifically designed to hold dirt and moisture close enough to the hull for long periods of time to induce rusting.
I did not put mine back - you could even come by and dig them out of the shed if you need a pattern. Even after a good long day of parading the fuel must get to the rotten old fuel pump to get hot enough to boil - no asbestos cover would have helped.
Also, with all of the muffler hardware and rear plate covering it up - the only person who would know it was not installed - you just drove over them!
Stewart