The salvage has been inhabited by a numerous and strong group of super mutants. The location occupies a quite vast area, where you find a lot of valuable items. You only need to keep an eye out, thanks to which you miss no room or container.
In John Millers' house, to the South of the Salvage, you find a master safe.
More or less, in the center of the scrapyard, you find a flipped blue railway car. After you enter, you find a trapdoor into the vault. To get inside, you need to restore power supply first. The easiest way to do this is by following the cable to the generator. Inside, you find the Railway Rifle.
In the trailer atop the car wreck pile, thee is an issue of Tales of Junktown Jerky Vendor. Also, you find a mininuke these, as well as ammo and meds.
To the North-East of the scrapyard, there is the Red Rocket station. It is guarded by a big robot.