You can do it, as far as clearance issues are concerned, with no problems. You'd want 245/55's, though, not 50's, to keep your speedometer accurate. HOWEVER, 245's are at the absolute limit of what's considered safe on 7" rims, and I'd be a little worried about the possibility of a tire coming loose while I'm doing 70 mph on the highway. So I got 235's for my car...Kumho Ecsta's, which cost 69.95. I drove my car straight to the tire dealer after I picked it up and traded in the stock 215's for a $50 credit each. So the new tires ended up costing me about twenty bucks apiece. The least expensive 245's I saw were something like $180 each, which helped make my decision.
Check out
http://www.1010tires.com/tiresizecalculator.asp
for comparisons of tire sizes.