regardless where they come from, you always should replace them in sets. If they only have one, find a pair somewhere else. check the classifieds on this site. The only difference is the bracket as Kremit mentioned, but if you use struts from different sources, they will have different wear characteristics, and you'll have handling problems. Personally, I would never recommend installing used ones, especially with all the work involved with the front ones. But if you must, at least use a matched set.
