Having a used car inspected by a reputable repair shop — without ties to the dealership — is a very good idea. Having a salvage auto inspected before you buy is absolutely indispensable. Don't consider buying without it.
In addition to offering peace of mind when buying a salvage car that's already been reconstructed, an inspection can tell you exactly how much you'll be putting into repairs on a car that still needs to be rebuilt. If possible, have the inspection done at the body shop you plan to use for repairs so you'll be on the same page.
Finally, a pre-purchase inspection can pay for itself. What dealer comprehensively lists each and every wear, tear, leak, ding, dent and question mark? After your inspection, use the findings to ask the dealer for an additional reduction in price.