The "crash switch", or inertia switch is located under the spare wheel on the 2wd cossie, need to lift the wheel to access it, has a white button that pops up if tripped, it is a knock sensitive device designed to cut the fuel in the event of a major collision.
The relay pictured is a ford relay at a major over inflated price, it will do the job, just as well as a £3 brand new relay.
All you need is a standard switching relay which will have the numbers 30/85/86/87 on it, just go into a car accessory shop, another type of relay can be used called a changeover relay which will just have a extra "87a" on it, this just switches output from 87 to 87a when switched that's all so can be used no problem.
tabetha