Oh, I'm not talking about restoring one to operational condition. The problems you mention were only due to the neccessity to withstand extreme heat. Airshow passes wouldn't involve M3+ flight. Tank sealants, oil etc, would not need to withstand high temps, therefore alternatives could be used (and have been in the past). A restored SR-71 wouldn't even need to use JP-7, as J-58's could happily drink JP-4 or 5 (limiting the aircraft to M1.5).L:
Major non conforming re-engineering to the design (thus astronomical cost)
Thats what some folk said about the Vulcan. The only limit is the mind... well, and dosh, and US gov.
And the FAA and Lockhead Martin as DA.
The Vulcan will hopefully be blessed with corporate sponsorship now. However they have struggled, even with lottery money and rich benifactors.