I'm looking at a salvage '07 2500 that still would have 2 years left on the powertrain warranty. The damages are all stricktly sheet metal (lots) but there is no mechanical damage to the powertrain.
Does the warranty automatically become void after a vehicle is written off by an insurance company and the repaired vehicle subsequently carries a salvage title?

The warranty is void if the truck has been totaled.

Yes, all warranties by the dealer or voided, if there is any salvage or rebuilt brands on the title.

the only warranty that would be left is the federal emmisions warranty