I think you are missing the fact that they are one and the same. With the explorers, you can buy the shock, and simply swap it out. (Not that it's exactly simple to do) Or you can buy what's called a Quick Strut. The Quick Strut isn't exactly like car struts. All it is, is the shock and the spring packaged together. More money, but a lot quicker to install.
So, either you just replace the shock, and reuse your spring.
Or you replace both at once as a 'strut.'
Either way, the shock portion is the same.