Well, wheels, crank,(unless I can get by with my shimano stx) handlebars and brakes.
I am mainly worried about going out and buying a set of road wheels and they suddenly don't fit my frame.
You see, I am very new to this idea of building a bike, and I love the idea of doing so. What I want is a single speed bike built up from this old mountain bike. I think that a flip flop rear hub would be the right choice as I am not ready to go fixed gear in a new city. I would also like at least one brake for safety. (call me a wuss, like I said I am new here.)
Is the frame geometry of the bike going to be really bad for this type of riding. Again, I have been riding a mountian bike for many years, but I am new to the idea making your own bike, and know frame geometry etc.