Nose piece, depends on how narrow you want to run the front width. If you can get your tires to be under 38″ from outside to outside, then look into getting a new nose piece. If not, stick with the 40″.
Not sure on the pipe, but it depends on the engine and gearing you are utilizing. Something that is for top end is better, depends on what you have.
Tires are open, and depends on what you prefer. Some use the 5″ wheels, some use 6″. Hoosier seems to be among the popular brands now.