Mountain bikes usually have long top tubes and stems which is important here because it may be difficult for you to find a road bike with enough reach. Mountain bikes usually have long cranks and there are now 29er bikes, which mean bigger wheels as well. A bit more reach can be added with drop bars instead of flat bars

i'm 6'5" and i feel like I'm at the edge of bike sizes. It isnt very often I see a large bike on CL, but when I do they are usually low end and trashed. I found one in decent shape but it is low end. It's not often I get a frame my size so I chose to build it up anyway.