Hi, I'd agree with comprex that you need to think about boots for sure. You're really pushing the envelope on equipment at your size and you may need to find some more specialized skis and boots. If your local shops only have standard, general-population ski equipment, you should probably look elsewhere.
XC skis need to maintain proper camber through both the kick and glide phase, so flex testing is a must. A good shop will put you on a flex tester, or, at the very least, do the paper-under-the-skis test. DON'T buy skis without some kind of assurance that they are right for your size (and not just some salesman saying they are). That said, skis do have "flavors", and FWIW I find Karhus tend to run soft, which is not what you want at your height/weight.
I would argue that the correct equipment is even more important in XC than in alpine skiing; it can make it a great gliding experience or reduce it to either a slog or banana-peel misery. So getting it right really matters. If your local shops only deal with middle-of-the-road equipment and skills, try looking online at places like Skinny Skis or Cross Country Ski Shop. These guys will talk to you on the phone and do a weighted flex test in their shops before they sell you something.
I ski 40+ days a year XC, so I'm a bit biased, but I really hate for people to buy cheap/inappropriate equipment, then decide they don't like the experience because they have the wrong stuff. Many folks just go buy skis as if they were buying something as simple as a jacket. You need to find the stuff that's right for you. I could offer you a few models that might be right, but it'd be better to get to know a salesperson that way. Tell your sales person what you think you will do (as comprex says, you probably want a ski that will fit in track) and make sure they are selling you stuff that fits you and your needs, not just the skis they have sitting around.